The code to unlock the door was the default code that comes with the lock and is supposed to be changed when the lock is installed (googling the lock brand will bring up the code, but anyone can probably guess what it is), i.e. as close as you can get to not actually locking the door. The hosting agency, Plays, completely refused to acknowledge the issue and claimed that the code could only be changed after we had checked out, which of course isn’t the case as the code can be changed at any time as long as you have the master code for the lock. In the end, a helpful person brought over a key that worked independently of the code lock; this was five hours after we had checked in, and after someone from the hosting agency had told us to leave the place, almost kicking us out for not accepting that the door couldn’t be properly locked.
Apart from that, the apartment was reasonable enough, if not entirely clean, especially not the kitchenware.
NB: If you're taller than about 1.68 m you cannot walk upright in the apartment as the opening between the sleeping area and the kitchen area is very low.