So with some friends we started playing on a world (on a server, hosted on Aternos if that matters) in creative in.. 1.17 or 1.18 I believe (also maybe it matters, there are a lot of command blocks). Up until 1.20, there were no problem at all, we played fine. Since the 1.20 update, when I connect to the server, it either crashes entirely (the console juste says "Player connected : [my username then my xuid]" and the server proceeds to stop), or it says this : https://mclo.gs/6qtPqYB , and then I still see the server loading screen, and the server bugs a lot for my friends (can't place blocks or anything, they can just move; like if the server crashed but not closed)

We tried to export/import the server to our own computers, and when my friends did so, they could play on the server, but when I joined them the minecraft app of the one hosting crashed.

When I tried to import the server, it sayed "Fail to import the world"

That was like a week ago, and now my friends too can't load the server on their pcs (same error message as me), however they can still play on the server.

We have made a lot of backups (like 20 of them in a year) and if I load a save from a long time ago (2022 for ex) and I teleport to certain coordinates (-500 100 -3000 and arround, It is possible that they are the coordinates where i left the server before updating to 1.20, but I'm not 100%), I crash

When I go to the same coordinates on the same seed (2021551997) in a blank new world, I don't crash