The issue is that ChunkPregen actually does, because otherwise your max world size is pretty easily defined.
The issue is since lithium adds a lot of extra info for optimization this leads to data corruption.
I will have to disable my override of your override.
What you should do, is implement a proper system for unloading points of interest.
Since there were people before you who ported this mod to 1.16 and this crash was found,
here is the patch what they have done and has proven to be working.
o/ Since this is a lithium port, eh yeah lithium is right now incompatible with ChunkPregenerator.
What is the problem. Minecraft by default never unloads Points of Interests. https://github.com/Asek3/Radium/blob/main/src/main/java/me/jellysquid/mods/lithium/mixin/ai/poi/SerializingRegionBasedStorageMixin.java#L54
The issue is that ChunkPregen actually does, because otherwise your max world size is pretty easily defined. The issue is since lithium adds a lot of extra info for optimization this leads to data corruption.
I will have to disable my override of your override. What you should do, is implement a proper system for unloading points of interest.
Since there were people before you who ported this mod to 1.16 and this crash was found, here is the patch what they have done and has proven to be working.
https://github.com/MaxNeedsSnacks/roadrunner/commit/d5d87ed50e36a56ff607a44afa98d9fae55de464 It would be nice if you could integrate this too so we can have a compat between our mods.
Sry if i am coming on to this a bit fast, its just this is like the third time i reported it ^^"