As soon as the update came out, me and my friends went on one of our realms to go to the nether. We found that if we went on, even without going to the nether, it kept crashing and almost everything we had done in the minutes before that was gone. It would say something like "Server closed." every time.

Edit: Please don't move my post into 1.15 again, it was 1.16 that I was using.