ConcurrentModificationError when opening a chest

[feoranis26]

I have this crash when I open any chests. I can't play on my survival world now. I wasn't able to get any reproduction steps because minecraft takes 20 minutes to open.

java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
	at java.util.ArrayList$Itr.next(ArrayList.java:851)
	at com.rwtema.extrautils2.items.ItemUnstableIngots.checkForExplosion(ItemUnstableIngots.java:192)
	at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_1937_ItemUnstableIngots_checkForExplosion_PlayerTickEvent.invoke(.dynamic)
	at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
	at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
	at net.minecraftforge.fml.common.FMLCommonHandler.onPlayerPreTick(FMLCommonHandler.java:365)
	at net.minecraft.entity.player.EntityPlayer.func_70071_h_(EntityPlayer.java:190)
	at net.minecraft.entity.player.EntityPlayerMP.func_71127_g(EntityPlayerMP.java:382)
	at net.minecraft.network.NetHandlerPlayServer.func_73660_a(NetHandlerPlayServer.java:173)
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher$1.func_73660_a(NetworkDispatcher.java:209)
	at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:285)
	at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:180)
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:790)
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668)
	at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:185)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
	at java.lang.Thread.run(Thread.java:745)

Running extrautils 1.9.9 on ATM3

[feoranis26]

Disabling unstable ingots in the config seems to fix this for now.