We have a project ozone 3 minecraft server that was working really well until today. For some reason, the server keeps crashing the moment that two of us join. It seems to be fine when one person joins, but the moment the next person joins, it crashes. I tried loading multiple backups and were getting the same crashes. The weird thing is that the server was running fine during those backups, so the crashing doesn't make sense to me when reverting to those backups. I have a full crash log attached, as well as the backups all saved locally in case the issue is a quick fix. I cant recall what we were doing during the first crash, but it was nothing out of the ordinary, and the crash kept happening going back to previous backups so I cant put my finger on it. It seems to run fine if only one of us joins, regardless of who joins first. The moment the second person joins, it crashes almost instantly.

Here is the crash log: https://pastebin.com/4YfpmBEp

Seemingly fixed, I had to delete the advancements json file for every player in the server as this seemed to be the error. After deleting the files and reloading the server, we were able to join back in.