Our Enigmatica 2 Expert v1.14 server has been seeing random AE2 crashes throughout the past week.
I have crash reports for rv6.stable build 2 and rv6.alpha build 4. Here they are respectively.
https://gist.github.com/Quantum001/dc638b4e88ead14a5b8e441d7ff91684
https://gist.github.com/Quantum001/b3d124a23e99736863b07f049ed9c632

Both versions throw the same exception, which crashes the server.
Description: Exception in server tick loop

java.util.ConcurrentModificationException
at java.util.LinkedHashMap$LinkedHashIterator.remove(LinkedHashMap.java:732)
at appeng.me.cache.EnergyGridCache.extractProviderPower(EnergyGridCache.java:316)
at appeng.me.cache.EnergyGridCache.extractAEPower(EnergyGridCache.java:248)
at appeng.me.cache.EnergyGridCache.onUpdateTick(EnergyGridCache.java:199)
at appeng.me.GridCacheWrapper.onUpdateTick(GridCacheWrapper.java:43)
at appeng.me.Grid.update(Grid.java:280)
at appeng.hooks.TickHandler.onTick(TickHandler.java:228)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_1681_TickHandler_onTick_TickEvent.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.onPostServerTick(FMLCommonHandler.java:266)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:712)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
at java.lang.Thread.run(Thread.java:748)

I am not aware or any specific actions that cause the crash, it seems to be arbitrary.

• Minecraft Version: 1.12.2
• AE2 Version: rv6.stable build 2 and rv6.alpha build 4
• Forge Version: 14.23.5.2768
• Enigmatica 2 Expert v1.41

Duplicate of #3800