The hosts failed to inform us that the bottom lock was broken (and they admitted this as well). Therefore, we were locked out of the apartment for quite some time at 2am in the dark alleyway where guests are required to enter. After phone calls didn't go through to the phone number provided and messages via text/airBnB weren't answered, we finally went to the front door. We knocked for a while, until someone who lives upstairs in the house came to the door, reluctantly let us in, and gave us a nasty attitude.
On the plus side, the host had been reachable before then and was flexible with check-in time. Check out time was flexible as well, but after the poor experience with being locked out, we decided to just leave as quickly as we could.