Stuck doors: if the door stays stuck, the locking pins on the hinged side of the door may be in contact with the body of the safe, putting force on the locking mechanism and the lock tongue.
The solution is to take the load off the bolt: press the handle immediately after entering the code while in the closed position, and the latch will open normally. Removing the load from the tongue (for example by raising it slightly with a lever) helps.
Battery and emergency power: if the battery runs out, you can replace the battery external, provide emergency power using a 9V battery or use the provided emergency key (Kaba Mauer Combi B90).