diff --git a/app/services/door.py b/app/services/door.py
index 5b36ea7..3d123e7 100644
--- a/app/services/door.py
+++ b/app/services/door.py
@@ -133,4 +133,4 @@ def checkAccess(key: str, db: Session):
         logger.info("No more auths found")
         return False
     except exc.NoResultFound:
-        raise Exception("No Access with that key found, this might be a db error")
+        raise Exception("No AccessAuth with that key found!")
diff --git a/app/services/scanner.py b/app/services/scanner.py
index 13ac085..475992b 100644
--- a/app/services/scanner.py
+++ b/app/services/scanner.py
@@ -77,7 +77,7 @@ def readFileOnCard(desfire: DESFire):
         assert len(applications) == 1
         assert applications[0] == get_list(MIFARE_APP_ID)
     except AssertionError:
-        logger.error("No application found!")
+        logger.error("No application found! The card must be registered first!")
         time.sleep(4)
         return
     # Then use the key derivation with that uid, the appid, the sysid
@@ -125,23 +125,13 @@ def DeleteCard():
         aes_null_key = DESFireKey(aes_keysettings, "00" * 16)
 
         desfire.select_application(0x0)
-
-        try:
-            try:
-                logger.debug("Auth1")
-                desfire.authenticate(0x0, aes_master_key)
-            except:
-                logger.debug("Auth2")
-                desfire.authenticate(0x0, aes_null_key)
-        except:
-            logger.debug("Auth3")
-            desfire.authenticate(0x0, desKey)
+        desfire.authenticate(0x0, desKey)
 
         applications = desfire.get_application_ids()
         logger.debug(f"Applications: {applications}")
         if len(applications) == 0:
             raise HTTPException(
-                status_code=status.HTTP_410_GONE, detail="No applications on card"
+                status_code=status.HTTP_410_GONE, detail="Card is empty."
             )
 
         desfire.select_application(MIFARE_APP_ID)
@@ -185,6 +175,13 @@ def WriteNewCard():
         # get uid
         uid = desfire.get_real_uid()
 
+        applications = desfire.get_application_ids()
+        logger.debug(f"Applications: {applications}")
+        if len(applications) >= 1:
+            raise HTTPException(
+                status_code=status.HTTP_409_CONFLICT, detail="This Card already has a key!"
+            )
+
         # Set default key
         logger.debug("Setting default key...")
         desfire.change_default_key(aes_null_key, 0x0)
@@ -270,12 +267,12 @@ def WriteNewCard():
         return key, to_hex_string(data=uid, separator=":")
 
     except Exception as e:
-        logger.error(f"Error in write function: {e}", exc_info=True)
+        logger.error(f"Error in write function: {e}", exc_info=False)
+        scannerThread.start()
         raise HTTPException(
             status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail=f"Error: {e}"
         )
 
-
 class BackgroundScanner:
     def __init__(self, db):
         self.db = db
@@ -310,7 +307,7 @@ class BackgroundScanner:
                     logger.debug("READY after timout")
 
             except Exception as e:
-                logger.error(f"Error in scan function: {e}", exc_info=True)
+                logger.error(f"Error in function _scan_loop: {e}", exc_info=False)
                 time.sleep(6)
 
     def _read_card(self):
@@ -326,7 +323,7 @@ class BackgroundScanner:
             rdata = readFileOnCard(desfire=desfire)
             return rdata
         except Exception as e:
-            logger.error(f"something went wrong: {e}")
+            logger.error(f"Error in function _read_card: {e}", exc_info=False)
             time.sleep(5)
 
     def _check_db(self, key):