crash-2024-09-21_09.56.51-client.txt

The crash was caused by a java.util.ConcurrentModificationException during the initialization of CodeChickenLib. Probably Multiple threads or processes attempt to modify a collection (such as a HashMap) simultaneously without proper synchronization.

1.12.2 is not supported anymore.

The map in question is not owned by CCL, it's FMLDeobfuscatingRemapper.rawFieldMaps.

I recommend removing some of your core mods until you find the offending mod.