I'm not really sure if this had to go into Modder Support cause I've never seen this crash and I'm pretty sure its caused by forge and not my mod. I got this crash report on my issue tracker and from what I'm seeing its forge's fault:

Caused by: net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerException: Exception in class transformer net.minecraftforge.fml.common.asm.transformers.SideTransformer@58d63b16 from coremod FMLCorePlugin
	at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:262)
	at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279)
	at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176)
	... 19 more
Caused by: java.lang.RuntimeException: Attempted to load class terrails/terracore/registry/client/ICustomModel for invalid side SERVER
	at net.minecraftforge.fml.common.asm.transformers.SideTransformer.transform(SideTransformer.java:62)
	at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:258)
	... 21 more

By the looks of it its trying to load ICustomModel interface in my library mod on server side (the interface is annotated with Side.CLIENT), I'm using that interface only in ModelRegistryEvent to register models for blocks/items

Edited April 15, 20187 yr by Terrails
added link to the event

Alright I know how I'll do it then, Thanks!