I'm running a server on 1.20.1 Forge 47.7.0 with Map Atlases 6.0.12 and a handful of other mods. I was exploring (alone on the server) when suddenly the game crashed. When I try to log back in, the game cannot load a SINGLE chunk (occasionally it loads the lower part of one) and crashes after 60 seconds because of a tick taking too long. The crash report suspects Map Atlases and after looking at the server's console : the crash happens after Map Atlases encounter an error ("couldn't find map id [number]"). Maybe my atlas is trying to map chunks that has not generated yet, or maybe it's missing a map it should have. I wasn't able to replicate this bug in another world. I don't know how to get my server back, everytime I join I get 60 seconds of me floating in a blank space and then I'm kicked out. Here's the crash report :

crash-2025-08-19_21.08.49-server.txt

It's some kind of deadlock issue where it ends up waiting on a chunk that is also waiting on something else. Thing I've never heard of this happen with mod alone, altho I was afraid something similar might have happen when multiple players were using same map but since you were alone that can't be it. It must be indirectly conflicting with some mod of sorts, do you have anything that alters how chunks are loaded? For a temp fix turn off async updates in the config but map wil then map out at vanilla speed

I removed the NBT file of map atlases on the computer I was using to play. It solved the issue, at least the chunk loading part. So I guess the problem was client side, my atlas was trying to reach a map the server didn't have. I did have a mod that affected chunk generation (I think ModernFix does that) so maybe that's the source of the problem. I'm closing the issue because another mod was likely involved as you said.