1.16.5 Dedicated server crash on autocrafting - Exception in server tick loop java.util.ConcurrentModificationException: null at appeng.util.item.ItemList$ChainedIterator.next

[ProsperCraft]

Describe the bug
A player on our server says he was autocrafting Mekanim things, and the server went down, he was the only player on at the time.

To Reproduce
Asking him for steps to reproduce.

Additional context
Crashlog-
https://gist.github.com/ProsperCraft/82ef431b0d11ec862898bf98e0bbaeea

Environment
appliedenergistics2-8.3.0-alpha.3
forge-1.16.5-36.1.2
Dedicated server.
TownCraft TWO for 1.16.5 modpack

[shartte]

Do you know what the player was crafting?

[ProsperCraft]

Mekanism power cables, but when they did it again, it did not crash.

[yueh]

performant might also be a cause here.

[ProsperCraft]

It happened again, here is the crash report
https://gist.github.com/ProsperCraft/2bfca0458235159f2e9f4ed2230ce128
Here is the debug log-
https://gist.github.com/ProsperCraft/3478b7575ba6941a58b439533f5a5bd9

[shartte]

@ProsperCraft We've just pushed alpha.4 that includes more debugging code to hopefully track the root cause of this down.
In the meantime, I presume the craft that caused this was the same again? Can you describe the pattern that the player is using to craft?

[zpprsprk]

I just experienced a similar issue. I was running version alpha.4 and this is the part of the server log file when the crash happened.
https://gist.github.com/zpprsprk/57247faf16fe6affb473826e5d9f4fa3
Crash report: https://gist.github.com/zpprsprk/555b018f2e9d62dae3480e52d18a93d9
I was auto crafting with a mekanism ultimate smelting factory. The pattern was a processing pattern for 64 exnihilo nickel ore chunks to 64 nickel ingots. It first happened when I requested 1001 ingots (it said it would do 1024). After restarting the server, I asked for 128 with no issues, then 1024 (exactly) with no issues, then again 1001 (that it said it would do 1024 again) and triggered the crash again.

[yueh]

@zpprsprk Thanks, could reproduce it thanks to the description