diff --git a/lib/Db/AssignedUsersMapper.php b/lib/Db/AssignedUsersMapper.php
index e9323811f..a7e0ea0b6 100644
--- a/lib/Db/AssignedUsersMapper.php
+++ b/lib/Db/AssignedUsersMapper.php
@@ -40,6 +40,12 @@ class AssignedUsersMapper extends DeckMapper implements IPermissionMapper {
 		$this->userManager = $userManager;
 	}
 
+	/**
+	 * FIXME: rename this since it returns multiple entities otherwise the naming is confusing with Entity::find
+	 *
+	 * @param $cardId
+	 * @return array|Entity
+	 */
 	public function find($cardId) {
 		$sql = 'SELECT * FROM `*PREFIX*deck_assigned_users` ' .
 			'WHERE `card_id` = ?';
diff --git a/lib/Db/AttachmentMapper.php b/lib/Db/AttachmentMapper.php
index 4ead87510..2ccae3be8 100644
--- a/lib/Db/AttachmentMapper.php
+++ b/lib/Db/AttachmentMapper.php
@@ -39,6 +39,13 @@ class AttachmentMapper extends DeckMapper implements IPermissionMapper {
 	private $userManager;
 	private $qb;
 
+	/**
+	 * AttachmentMapper constructor.
+	 *
+	 * @param IDBConnection $db
+	 * @param CardMapper $cardMapper
+	 * @param IUserManager $userManager
+	 */
 	public function __construct(IDBConnection $db, CardMapper $cardMapper, IUserManager $userManager) {
 		parent::__construct($db, 'deck_attachment', Attachment::class);
 		$this->cardMapper = $cardMapper;
@@ -60,7 +67,17 @@ class AttachmentMapper extends DeckMapper implements IPermissionMapper {
 
 		$cursor = $qb->execute();
 		$row = $cursor->fetch(PDO::FETCH_ASSOC);
+		if($row === false) {
+			$cursor->closeCursor();
+			throw new DoesNotExistException('Did expect one result but found none when executing' . $qb);
+		}
+
+		$row2 = $cursor->fetch();
 		$cursor->closeCursor();
+		if($row2 !== false ) {
+			throw new MultipleObjectsReturnedException('Did not expect more than one result when executing' . $query);
+		}
+
 		return $this->mapRowToEntity($row);
 	}
 
@@ -87,6 +104,11 @@ class AttachmentMapper extends DeckMapper implements IPermissionMapper {
 		return $entities;
 	}
 
+	/**
+	 * @param null $cardId
+	 * @param bool $withOffset
+	 * @return array
+	 */
 	public function findToDelete($cardId = null, $withOffset = true) {
 		// add buffer of 5 min
 		$timeLimit = time() - (60 * 5);
diff --git a/lib/Service/AttachmentService.php b/lib/Service/AttachmentService.php
index a2bbcbc0a..53f89f518 100644
--- a/lib/Service/AttachmentService.php
+++ b/lib/Service/AttachmentService.php
@@ -123,6 +123,10 @@ class AttachmentService {
 		return $attachments;
 	}
 
+	/**
+	 * @param $cardId
+	 * @return int|mixed
+	 */
 	public function count($cardId) {
 		$count = $this->cache->get('card-' . $cardId);
 		if (!$count) {
@@ -132,6 +136,14 @@ class AttachmentService {
 		return $count;
 	}
 
+	/**
+	 * @param $cardId
+	 * @param $type
+	 * @param $data
+	 * @return Attachment|\OCP\AppFramework\Db\Entity
+	 * @throws NoPermissionException
+	 * @throws StatusException
+	 */
 	public function create($cardId, $type, $data) {
 		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
 
@@ -172,7 +184,11 @@ class AttachmentService {
 	 * @param $cardId
 	 * @param $attachmentId
 	 * @return Response
+	 * @throws \OCA\Deck\NotFoundException
+	 * @throws NoPermissionException
 	 * @throws NotFoundException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
 	 */
 	public function display($cardId, $attachmentId) {
 		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_READ);
diff --git a/lib/Service/BoardService.php b/lib/Service/BoardService.php
index 1ce4f546b..6b250fb4a 100644
--- a/lib/Service/BoardService.php
+++ b/lib/Service/BoardService.php
@@ -75,6 +75,9 @@ class BoardService {
 		$this->userId = $userId;
 	}
 
+	/**
+	 * @return array
+	 */
 	public function findAll() {
 		$userInfo = $this->getBoardPrerequisites();
 		$userBoards = $this->boardMapper->findAllByUser($userInfo['user']);
@@ -102,6 +105,13 @@ class BoardService {
 		return array_values($result);
 	}
 
+	/**
+	 * @param $boardId
+	 * @return Board
+	 * @throws DoesNotExistException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function find($boardId) {
 		$this->permissionService->checkPermission($this->boardMapper, $boardId, Acl::PERMISSION_READ);
 		/** @var Board $board */
@@ -124,6 +134,9 @@ class BoardService {
 		return $board;
 	}
 
+	/**
+	 * @return array
+	 */
 	private function getBoardPrerequisites() {
 		$groups = $this->groupManager->getUserGroupIds(
 			$this->userManager->get($this->userId)
@@ -134,6 +147,14 @@ class BoardService {
 		];
 	}
 
+	/**
+	 * @param $mapper
+	 * @param $id
+	 * @return bool
+	 * @throws DoesNotExistException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function isArchived($mapper, $id) {
 		try {
 			$boardId = $id;
@@ -150,6 +171,14 @@ class BoardService {
 		return $board->getArchived();
 	}
 
+	/**
+	 * @param $mapper
+	 * @param $id
+	 * @return bool
+	 * @throws DoesNotExistException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function isDeleted($mapper, $id) {
 		try {
 			$boardId = $id;
@@ -167,7 +196,12 @@ class BoardService {
 	}
 
 
-
+	/**
+	 * @param $title
+	 * @param $userId
+	 * @param $color
+	 * @return \OCP\AppFramework\Db\Entity
+	 */
 	public function create($title, $userId, $color) {
 		$board = new Board();
 		$board->setTitle($title);
@@ -203,6 +237,13 @@ class BoardService {
 
 	}
 
+	/**
+	 * @param $id
+	 * @return Board
+	 * @throws DoesNotExistException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function delete($id) {
 		$this->permissionService->checkPermission($this->boardMapper, $id, Acl::PERMISSION_READ);
 		$board = $this->find($id);
@@ -211,6 +252,13 @@ class BoardService {
 		return $board;
 	}
 
+	/**
+	 * @param $id
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws DoesNotExistException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function deleteUndo($id) {
 		$this->permissionService->checkPermission($this->boardMapper, $id, Acl::PERMISSION_READ);
 		$board = $this->find($id);
@@ -218,12 +266,29 @@ class BoardService {
 		return $this->boardMapper->update($board);
 	}
 
+	/**
+	 * @param $id
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws DoesNotExistException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function deleteForce($id) {
 		$this->permissionService->checkPermission($this->boardMapper, $id, Acl::PERMISSION_READ);
 		$board = $this->find($id);
 		return $this->boardMapper->delete($board);
 	}
 
+	/**
+	 * @param $id
+	 * @param $title
+	 * @param $color
+	 * @param $archived
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws DoesNotExistException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function update($id, $title, $color, $archived) {
 		$this->permissionService->checkPermission($this->boardMapper, $id, Acl::PERMISSION_MANAGE);
 		$board = $this->find($id);
@@ -235,6 +300,16 @@ class BoardService {
 	}
 
 
+	/**
+	 * @param $boardId
+	 * @param $type
+	 * @param $participant
+	 * @param $edit
+	 * @param $share
+	 * @param $manage
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws \OCA\Deck\NoPermissionException
+	 */
 	public function addAcl($boardId, $type, $participant, $edit, $share, $manage) {
 		$this->permissionService->checkPermission($this->boardMapper, $boardId, Acl::PERMISSION_SHARE);
 		$acl = new Acl();
@@ -253,6 +328,16 @@ class BoardService {
 		return $newAcl;
 	}
 
+	/**
+	 * @param $id
+	 * @param $edit
+	 * @param $share
+	 * @param $manage
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws DoesNotExistException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function updateAcl($id, $edit, $share, $manage) {
 		$this->permissionService->checkPermission($this->aclMapper, $id, Acl::PERMISSION_SHARE);
 		/** @var Acl $acl */
@@ -264,6 +349,13 @@ class BoardService {
 		return $this->aclMapper->update($acl);
 	}
 
+	/**
+	 * @param $id
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws DoesNotExistException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function deleteAcl($id) {
 		$this->permissionService->checkPermission($this->aclMapper, $id, Acl::PERMISSION_SHARE);
 		/** @var Acl $acl */
diff --git a/lib/Service/CardService.php b/lib/Service/CardService.php
index fcf691ecc..ad54f819d 100644
--- a/lib/Service/CardService.php
+++ b/lib/Service/CardService.php
@@ -89,6 +89,13 @@ class CardService {
 		return $cards;
 	}
 
+	/**
+	 * @param $cardId
+	 * @return \OCA\Deck\Db\RelationalEntity
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function find($cardId) {
 		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_READ);
 		$card = $this->cardMapper->find($cardId);
@@ -100,7 +107,16 @@ class CardService {
 	}
 
 	/**
+	 * @param $title
+	 * @param $stackId
+	 * @param $type
 	 * @param integer $order
+	 * @param $owner
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
 	 */
 	public function create($title, $stackId, $type, $order, $owner) {
 		$this->permissionService->checkPermission($this->stackMapper, $stackId, Acl::PERMISSION_EDIT);
@@ -117,6 +133,14 @@ class CardService {
 
 	}
 
+	/**
+	 * @param $id
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function delete($id) {
 		$this->permissionService->checkPermission($this->cardMapper, $id, Acl::PERMISSION_EDIT);
 		if ($this->boardService->isArchived($this->cardMapper, $id)) {
@@ -128,6 +152,21 @@ class CardService {
 		return $card;
 	}
 
+	/**
+	 * @param $id
+	 * @param $title
+	 * @param $stackId
+	 * @param $type
+	 * @param $order
+	 * @param $description
+	 * @param $owner
+	 * @param $duedate
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function update($id, $title, $stackId, $type, $order, $description, $owner, $duedate, $deletedAt) {
 		$this->permissionService->checkPermission($this->cardMapper, $id, Acl::PERMISSION_EDIT);
 		if ($this->boardService->isArchived($this->cardMapper, $id)) {
@@ -148,6 +187,15 @@ class CardService {
 		return $this->cardMapper->update($card);
 	}
 
+	/**
+	 * @param $id
+	 * @param $title
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function rename($id, $title) {
 		$this->permissionService->checkPermission($this->cardMapper, $id, Acl::PERMISSION_EDIT);
 		if ($this->boardService->isArchived($this->cardMapper, $id)) {
@@ -161,6 +209,16 @@ class CardService {
 		return $this->cardMapper->update($card);
 	}
 
+	/**
+	 * @param $id
+	 * @param $stackId
+	 * @param $order
+	 * @return array
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function reorder($id, $stackId, $order) {
 		$this->permissionService->checkPermission($this->cardMapper, $id, Acl::PERMISSION_EDIT);
 		if ($this->boardService->isArchived($this->cardMapper, $id)) {
@@ -192,6 +250,14 @@ class CardService {
 		return $result;
 	}
 
+	/**
+	 * @param $id
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function archive($id) {
 		$this->permissionService->checkPermission($this->cardMapper, $id, Acl::PERMISSION_EDIT);
 		if ($this->boardService->isArchived($this->cardMapper, $id)) {
@@ -202,6 +268,14 @@ class CardService {
 		return $this->cardMapper->update($card);
 	}
 
+	/**
+	 * @param $id
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function unarchive($id) {
 		$this->permissionService->checkPermission($this->cardMapper, $id, Acl::PERMISSION_EDIT);
 		if ($this->boardService->isArchived($this->cardMapper, $id)) {
@@ -212,6 +286,14 @@ class CardService {
 		return $this->cardMapper->update($card);
 	}
 
+	/**
+	 * @param $cardId
+	 * @param $labelId
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function assignLabel($cardId, $labelId) {
 		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
 		if ($this->boardService->isArchived($this->cardMapper, $cardId)) {
@@ -224,6 +306,14 @@ class CardService {
 		$this->cardMapper->assignLabel($cardId, $labelId);
 	}
 
+	/**
+	 * @param $cardId
+	 * @param $labelId
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function removeLabel($cardId, $labelId) {
 		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
 		if ($this->boardService->isArchived($this->cardMapper, $cardId)) {
@@ -236,6 +326,13 @@ class CardService {
 		$this->cardMapper->removeLabel($cardId, $labelId);
 	}
 
+	/**
+	 * @param $cardId
+	 * @param $userId
+	 * @return bool|null|\OCP\AppFramework\Db\Entity
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function assignUser($cardId, $userId) {
 		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
 		$assignments = $this->assignedUsersMapper->find($cardId);
@@ -257,6 +354,14 @@ class CardService {
 		return $this->assignedUsersMapper->insert($assignment);
 	}
 
+	/**
+	 * @param $cardId
+	 * @param $userId
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws NotFoundException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function unassignUser($cardId, $userId) {
 		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
 		$assignments = $this->assignedUsersMapper->find($cardId);
diff --git a/lib/Service/DefaultBoardService.php b/lib/Service/DefaultBoardService.php
index f79b8d24e..82fc02fa5 100644
--- a/lib/Service/DefaultBoardService.php
+++ b/lib/Service/DefaultBoardService.php
@@ -55,8 +55,14 @@ class DefaultBoardService {
 		$this->boardMapper = $boardMapper;
 		$this->l10n = $l10n;
     }
-    
-    public function checkFirstRun($userId, $appName) {        
+
+	/**
+	 * @param $userId
+	 * @param $appName
+	 * @return bool
+	 * @throws \OCP\PreConditionNotMetException
+	 */
+	public function checkFirstRun($userId, $appName) {
 		$firstRun = $this->config->getUserValue($userId, $appName, 'firstRun', 'yes');
 		$userBoards = $this->boardMapper->findAllByUser($userId);
 		
@@ -68,7 +74,17 @@ class DefaultBoardService {
 		return false;
     }
 
-    public function createDefaultBoard($title, $userId, $color) {
+	/**
+	 * @param $title
+	 * @param $userId
+	 * @param $color
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCA\Deck\StatusException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
+	public function createDefaultBoard($title, $userId, $color) {
         $defaultBoard = $this->boardService->create($title, $userId, $color);
         $defaultStacks = [];
         $defaultCards = [];
diff --git a/lib/Service/FileService.php b/lib/Service/FileService.php
index a122d76c5..543371bf2 100644
--- a/lib/Service/FileService.php
+++ b/lib/Service/FileService.php
@@ -142,6 +142,11 @@ class FileService implements IAttachmentService {
 		return $file;
 	}
 
+	/**
+	 * @param Attachment $attachment
+	 * @throws NotPermittedException
+	 * @throws StatusException
+	 */
 	public function create(Attachment $attachment) {
 		$file = $this->getUploadedFile();
 		$folder = $this->getFolder($attachment);
@@ -176,6 +181,10 @@ class FileService implements IAttachmentService {
 		$attachment->setLastModified(time());
 	}
 
+	/**
+	 * @param Attachment $attachment
+	 * @throws NotPermittedException
+	 */
 	public function delete(Attachment $attachment) {
 		try {
 			$file = $this->getFileForAttachment($attachment);
@@ -202,6 +211,11 @@ class FileService implements IAttachmentService {
 		return $cardFolder->get($attachment->getData());
 	}
 
+	/**
+	 * @param Attachment $attachment
+	 * @return FileDisplayResponse|\OCP\AppFramework\Http\Response|StreamResponse
+	 * @throws \Exception
+	 */
 	public function display(Attachment $attachment) {
 		$file = $this->getFileFromRootFolder($attachment);
 		if (method_exists($file, 'fopen')) {
diff --git a/lib/Service/LabelService.php b/lib/Service/LabelService.php
index 2bb910083..2b0a640be 100644
--- a/lib/Service/LabelService.php
+++ b/lib/Service/LabelService.php
@@ -44,11 +44,28 @@ class LabelService {
 		$this->boardService = $boardService;
 	}
 
+	/**
+	 * @param $labelId
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function find($labelId) {
 		$this->permissionService->checkPermission($this->labelMapper, $labelId, Acl::PERMISSION_READ);
 		return $this->labelMapper->find($labelId);
 	}
 
+	/**
+	 * @param $title
+	 * @param $color
+	 * @param $boardId
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function create($title, $color, $boardId) {
 		$this->permissionService->checkPermission(null, $boardId, Acl::PERMISSION_MANAGE);
 		if ($this->boardService->isArchived(null, $boardId)) {
@@ -61,6 +78,14 @@ class LabelService {
 		return $this->labelMapper->insert($label);
 	}
 
+	/**
+	 * @param $id
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function delete($id) {
 		$this->permissionService->checkPermission($this->labelMapper, $id, Acl::PERMISSION_MANAGE);
 		if ($this->boardService->isArchived($this->labelMapper, $id)) {
@@ -69,6 +94,16 @@ class LabelService {
 		return $this->labelMapper->delete($this->find($id));
 	}
 
+	/**
+	 * @param $id
+	 * @param $title
+	 * @param $color
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function update($id, $title, $color) {
 		$this->permissionService->checkPermission($this->labelMapper, $id, Acl::PERMISSION_MANAGE);
 		if ($this->boardService->isArchived($this->labelMapper, $id)) {
diff --git a/lib/Service/PermissionService.php b/lib/Service/PermissionService.php
index 8b7e69d12..5dff31be8 100644
--- a/lib/Service/PermissionService.php
+++ b/lib/Service/PermissionService.php
@@ -31,6 +31,8 @@ use OCA\Deck\Db\IPermissionMapper;
 use OCA\Deck\Db\User;
 use OCA\Deck\NoPermissionException;
 use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\AppFramework\Db\Entity;
+use OCP\AppFramework\Db\MultipleObjectsReturnedException;
 use OCP\IGroupManager;
 use OCP\ILogger;
 use OCP\IUserManager;
@@ -114,41 +116,40 @@ class PermissionService {
 	 * @throws NoPermissionException
 	 */
 	public function checkPermission($mapper, $id, $permission) {
-		try {
-			$boardId = $id;
-			if ($mapper instanceof IPermissionMapper) {
-				$boardId = $mapper->findBoardId($id);
-			}
-			if ($boardId === null) {
-				// Throw NoPermission to not leak information about existing entries
-				throw new NoPermissionException('Permission denied');
-			}
-
-			if ($this->userIsBoardOwner($boardId)) {
-				return true;
-			}
-			$acls = $this->aclMapper->findAll($boardId);
-			$result = $this->userCan($acls, $permission);
-			if ($result) {
-				return true;
-			}
-
-		} catch (DoesNotExistException $exception) {
+		$boardId = $id;
+		if ($mapper instanceof IPermissionMapper) {
+			$boardId = $mapper->findBoardId($id);
+		}
+		if ($boardId === null) {
 			// Throw NoPermission to not leak information about existing entries
 			throw new NoPermissionException('Permission denied');
 		}
 
-		throw new NoPermissionException('Permission denied.');
+		if ($this->userIsBoardOwner($boardId)) {
+			return true;
+		}
 
+		$acls = $this->aclMapper->findAll($boardId);
+		$result = $this->userCan($acls, $permission);
+		if ($result) {
+			return true;
+		}
+
+		// Throw NoPermission to not leak information about existing entries
+		throw new NoPermissionException('Permission denied');
 	}
 
 	/**
 	 * @param $boardId
 	 * @return bool
-	 * @throws \OCP\AppFramework\Db\DoesNotExistException
 	 */
 	public function userIsBoardOwner($boardId) {
-		$board = $this->boardMapper->find($boardId);
+		try {
+			$board = $this->boardMapper->find($boardId);
+		} catch (DoesNotExistException $e) {
+		} catch (MultipleObjectsReturnedException $e) {
+			return false;
+		}
 		return $board && $this->userId === $board->getOwner();
 	}
 
@@ -192,19 +193,34 @@ class PermissionService {
 			$board = $this->boardMapper->find($boardId);
 		} catch (DoesNotExistException $e) {
 			return [];
+		} catch (MultipleObjectsReturnedException $e) {
+			return [];
 		}
+
 		$owner = $this->userManager->get($board->getOwner());
-		$users = [];
-		$users[$owner->getUID()] = new User($owner);
+		if ($owner === null) {
+			$this->logger->info('No owner found for board ' . $board->getId());
+		} else {
+			$users = [];
+			$users[$owner->getUID()] = new User($owner);
+		}
 		$acls = $this->aclMapper->findAll($boardId);
 		/** @var Acl $acl */
 		foreach ($acls as $acl) {
 			if ($acl->getType() === Acl::PERMISSION_TYPE_USER) {
 				$user = $this->userManager->get($acl->getParticipant());
+				if ($user === null) {
+					$this->logger->info('No user found for acl rule ' . $acl->getId());
+					continue;
+				}
 				$users[$user->getUID()] = new User($user);
 			}
 			if ($acl->getType() === Acl::PERMISSION_TYPE_GROUP) {
 				$group = $this->groupManager->get($acl->getParticipant());
+				if ($group === null) {
+					$this->logger->info('No group found for acl rule ' . $acl->getId());
+					continue;
+				}
 				foreach ($group->getUsers() as $user) {
 					$users[$user->getUID()] = new User($user);
 				}
diff --git a/lib/Service/StackService.php b/lib/Service/StackService.php
index c5bdb7a8d..ae0850dae 100644
--- a/lib/Service/StackService.php
+++ b/lib/Service/StackService.php
@@ -89,21 +89,29 @@ class StackService {
 		}
 	}
 
+	/**
+	 * @param $stackId
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function find($stackId) {
 		$stack = $this->stackMapper->find($stackId);
 		$cards = $this->cardMapper->findAll($stackId);
 		foreach ($cards as $cardIndex => $card) {
 			$assignedUsers = $this->assignedUsersMapper->find($card->getId());
 			$card->setAssignedUsers($assignedUsers);
-			if (array_key_exists($card->id, $labels)) {
-				$cards[$cardIndex]->setLabels($labels[$card->id]);
-			}
 			$card->setAttachmentCount($this->attachmentService->count($card->getId()));
 		}
 		$stack->setCards($cards);
 		return $stack;
 	}
 
+	/**
+	 * @param $boardId
+	 * @return array
+	 * @throws \OCA\Deck\NoPermissionException
+	 */
 	public function findAll($boardId) {
 		$this->permissionService->checkPermission(null, $boardId, Acl::PERMISSION_READ);
 		$stacks = $this->stackMapper->findAll($boardId);
@@ -118,6 +126,11 @@ class StackService {
 		return $stacks;
 	}
 
+	/**
+	 * @param $boardId
+	 * @return array
+	 * @throws \OCA\Deck\NoPermissionException
+	 */
 	public function findAllArchived($boardId) {
 		$this->permissionService->checkPermission(null, $boardId, Acl::PERMISSION_READ);
 		$stacks = $this->stackMapper->findAll($boardId);
@@ -135,7 +148,14 @@ class StackService {
 	}
 
 	/**
+	 * @param $title
+	 * @param $boardId
 	 * @param integer $order
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
 	 */
 	public function create($title, $boardId, $order) {
 		$this->permissionService->checkPermission(null, $boardId, Acl::PERMISSION_MANAGE);
@@ -150,6 +170,13 @@ class StackService {
 
 	}
 
+	/**
+	 * @param $id
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function delete($id) {
 		$this->permissionService->checkPermission($this->stackMapper, $id, Acl::PERMISSION_MANAGE);
 
@@ -162,7 +189,18 @@ class StackService {
 		return $stack;
 	}
 
-
+	/**
+	 * @param $id
+	 * @param $title
+	 * @param $boardId
+	 * @param $order
+	 * @param $deletedAt
+	 * @return \OCP\AppFramework\Db\Entity
+	 * @throws StatusException
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function update($id, $title, $boardId, $order, $deletedAt) {
 		$this->permissionService->checkPermission($this->stackMapper, $id, Acl::PERMISSION_MANAGE);
 		if ($this->boardService->isArchived($this->stackMapper, $id)) {
@@ -176,6 +214,14 @@ class StackService {
 		return $this->stackMapper->update($stack);
 	}
 
+	/**
+	 * @param $id
+	 * @param $order
+	 * @return array
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
 	public function reorder($id, $order) {
 		$this->permissionService->checkPermission($this->stackMapper, $id, Acl::PERMISSION_EDIT);
 		$stackToSort = $this->stackMapper->find($id);