Description of the issue:

Had a ConcurrentModificationException on startup (probably a race condition / timing related) after updating from ImmersiveEngineering-1.16.5-4.2.0-130 to ImmersiveEngineering-1.16.5-4.2.1-131.

Starting the game again did not crash.

Crashlog:

https://gist.github.com/MatthiasMann/d598815042b88af2600069370dd8d19e

Versions & Modlist

ImmersiveEngineering-1.16.5-4.2.1-131
forge-1.16.5-36.0.4