Server keeps crashing when a player goes into a certain area

I'm playing a modded server and whenever a player goes into or rejoins in a certain area, the server crashes. I don't know why and any help would be helpful.

When I join this is shown

[26May2021 17:23:23.289] [Server thread/WARN] [net.minecraft.world.server.ServerWorld/]: Trying to add entity with duplicated UUID a89a74b0-6763-4320-bbe6-0cc4c4d62c36. Existing minecraft:zombified_piglin#209, new: minecraft:zombified_piglin#211

Then this right after

[26May2021 17:23:24.402] [Server thread/ERROR] [net.minecraftforge.eventbus.EventBus/EVENTBUS]: Exception caught during firing event: null

If you need it, here is the log

I have already deleted all .json files in the files area, (Fixed someone else's server on a different Thread) I found 4

Please reply, I have been working on it for about 5 months

Ok I'll try that

How do I do that, I have looked at the forum on backups, but I can't find the backups tab

Ok so as the mod Epic Fight Mod only really adds cool looking fighting, I decided to delete it without backing up (Risky). Luckily I can now get on, thank you so much and the thread can be closed