File of version 1.1.0 (1.12.2) begins with a _ which causes crash on startup. Simply renaming it fixes this issue.

Thank you very much for the debug.log.

It appears to be an issue with JustEnoughIDs not supporting Mixin 0.8.3, The simplest solution is to just remove MixinBootstrap as JustEnoughIDs includes the Mixin library it and other mods should work fine without MixinBootstrap.

Technical Information:
JustEnoughIDs cannot access org.spongepowered.asm.mixin.transformer.MixinProcessor in Mixin 0.8.3 as the class was made package-private.
https://github.com/DimensionalDevelopment/JustEnoughIDs/blob/eeaae8c0ee9305e5bf876c949a5e00374ef90807/src/main/java/org/dimdev/jeid/mixin/init/MixinLoader.java#L60-L66

Sorry my internet is shit, here it is. It's probably because other mods i have but im not good in interpretating logs.
debug.zip

Can you provide the debug.log for the crash, The purpose of the underscore is to ensure MixinBootstrap is loaded first.

I'm the new maintainer of JEID, if someone can help me fix the issue I will get it released asap