JustEnoughIDs is incompatible with Optifine, especially in larger packs.

Noted example would be trying to use BSL shaders to add emissives to specific blocks in Stoneblock.

Steps:

1. Install stoneblock modpack
2. Install 1.12.2 optifine from Optifine's website
3. Download Sampsa's custom BSL shaders: BSL_Shaders.zip
4. Open a new world, place down an antiblock. They don't behave as they normally do (they are no longer emissive in the vanilla sense: same color regardless of light level), and they don't emit shader emissives or bloom.
5. Exit the instance, disable JEID, launch, create a new world, place down antiblocks. Note that they are now very shiny.

I believe this is because it is changing the ID of the block, though I have no clue as to how this is happening.