My key doesn’t always work when entering the flat/hallway.

It’s best to visit the caretaker, he can adjust your key.
My key doesn’t always work when entering my room.

You can request repairs via the website of De Key
I left my key to the hallway in my room, what can I do?

If you locked yourself out of your hallway, flat or bicycle shed, the first thing you can try is ask your flatmates. If they’re not home, it’s best to post a message on facebook asking if somebody from the board or the student caretakers is home to let you in again. However, we can’t guarantee that one of these people is home. In that case you’ll have to wait.
I left my key to my room in my room, what can I do?

If you left your key in your room the easiest thing would be to use your spare key. If you left that one in the room as well or don’t have it with you at the moment, you’ll have to call a company to open the door for you. Since this is your own fault, you have to pay for this and you can’t expect a compensation from De Key.
Is it possible to get an extra key for entering the hallway?
Yes this is posible, but it costs 30 euros and you have to give the key back when you move. The caretaker can do this for you.