Hi, I am a maintainer of Lithium, and I had several (2) users report a crash with Lithium + fabric-carpet + carpet-extra + other different mods.

The minecraft bug that unloadEntityFix is supposed to fix is no longer reproducible (comments at https://bugs.mojang.com/browse/MC-108469 ). I believe that the unloadEntityFix therefore causes double adding of entities to the world in some edge cases.

A sanity check in a Lithium optimization (EntityTrackerEngine code) threw an Exception due to an Entity (Skeleton, while dismounting something) being added twice. As fabric-carpet's unloadedEntityFix changes how entities are added to chunk sections, I asked them whether they are using the feature. Both users were using unloadEntityFix ( see CaffeineMC/lithium-fabric#119 and CaffeineMC/lithium-fabric#107 ).