java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
at java.util.ArrayList$Itr.next(Unknown Source)
at net.minecraft.world.World.func_175644_a(World.java:3015)
at futurepack.common.FPMain.onWorldTick(FPMain.java:542)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_449_FPMain_onWorldTick_WorldTickEvent.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:179)
at net.minecraftforge.fml.common.FMLCommonHandler.onPostWorldTick(FMLCommonHandler.java:272)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:774)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:666)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:239)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:524)
at java.lang.Thread.run(Unknown Source)

This should be fixed: 26.3.8

Thanks, its working now. Probably it happened cause of FoamFix option of deduplicateModelsMaxRecursion changed to 9.

yeah you should check the log, it now dont kill the game if it crashes but it sill does crash, so notice me if it spams the log with crashes or only sometimes.

here is my modlist

Ok the only thing I can say is: this crash was caused by some other mod modifing the entity list from another thread. but thats it. I also I think I c ant fix this on my side because this could happen any time soon again .