Minecraft Version

1.21.1

Immersive Engineering Version

12.4.2-194

How did it happen?

Server Crashed when I manually inserted raw copper inside the arc furnace.

Crash Log

https://gist.github.com/Pixal-Byte/d9400ecff88e7ba81a9d9f28bafcd21b

I would guess you aren't running on default configurations, and have possibly adjusted the speed or energy requirements for the Arc Furnace?

yeah. i've reset them and it's back to normal, it was a config issue.