Fleas;
We booked this place for an extended stay, and when we arrived, we found cat hair everywhere, including a thick matt of it on the rug. From the owner, we found out that a lady had stayed there for the previous three months with a cat.
This cat had fleas and had spread them all over the apartment. We asked the host for a solution - and the owner - who is not the host, came by and dropped off diatomaceous earth, which, due to the flea life cycle, can take weeks to eradicate fleas. The owner also asked for the cleaners to come back, which is excellent, but they needed to hire an exterminator and steam cleaner to get rid of the fleas quickly.
We should not have been expected to exterminate the fleas by vacuuming twice a day and putting down diatomaceous earth. This place had an infestation; we killed 20-30 fleas over our stay.
After we left the place and found a new Airbnb, we contacted the host to request a refund as no one should have to deal with a pest during a stay. In the end, it was up to us with Airbnb directly to sort the cancellation and refund.
To pre-emptively respond with any answer we might get to our feedback let me just say we provided the owner with photographic evidence and showed them the issue in person and they had the gull to say, "the owner is passing there is nothing seen that you are talking about, so actually, I would need a photo of the fleas you talk about before even thinking about making a refund." And asked us to cancel ourselves, which would not prompt a reimbursement.
In the end, we were lucky enough to find another place to stay for the month and be able to get out of there as soon as we could.