There is definitely something going on, @Bernie19 . I just had a conversation with Support because a guest requested an alteration to a system-blocked prep day. Saw it as open and available for the alteration, when it has been automatically blocked by the system for months. I had to decline, but it's no fun. Guest doesn't get what they want and thinks it is the host playing games or "not updating the calendar".
In my case I contacted AirbnbHelp through Twitter and got an answer 8 hours later. The answer is just that they will look at it and cannot give me a timeline for a resolution.
I would report your situation if you can. The more of us clamoring for a calendar fix, the faster (hopefully) it gets done.