Changelog
v1.11.3
- fixed incompatibility with FalseTweaks experimental threaded rendering
If you have a mixin-related error, try adding UniMixins!
Otherwise, try using the "+nomixin" version of Campfire Backport, which is linked as an additional file. It doesn't embed SpongePowered/Mixin 0.7.11. You will need a separate mixin-providing mod (such as UniMixins).