A nightmare - safety emergency, plus maintenance and comms problems. This was the worst experience we have ever had with an AirBNB apartment.
The prior tenant had not returned their key, which meant that our check-in was delayed. We were sent a key, but not told that the prior tenant still had their key. During the night (midnight!), my mother-in-law was intruded upon by an unknown person entering the apartment. Luckily she was not harmed, but was so disturbed that she could not sleep, and could no longer feel safe in the apartment. This is truly a nightmare scenario. We should not have been given access to the apartment until the key had been returned! A million terrible things could have happened.
Minor in comparison, but still major: the lift was broken (had to climb too many stairs), and that the balcony door did not lock. From Friday through to Sunday, the phone line went unanswered, and responses to AirBNB messages were slow.
It is a pity that poor management and poor maintenance made this such a bad experience. The apartments themselves could be good places to stay.