I've been experiencing problems with dates being unavailable for a couple of weeks now. For one case, the last two dates of five open were marked unavailable (not blocked) and I had a guest book the three nights. The guest wanted to extend two nights and attempted to do so and said she was only able to select one additional night; when I tried (as host) I was able to select both nights and change the booking accordingly (I think via the app, can't remember). So in that case, even though the the website calendar grayed the dates and showed them as unavailable they were bookable (at least via changing the booking end date as host).