• Clean up the API (Malte)
  • THIS IS A BREAKING CHANGE!
  • Don't expect addons to work without being updated!
    https://www.curseforge.com/minecraft/mc-mods/immersive-engineering/files/3326143

Here's a crash log and more information that will hopefully prove helpful:

Minecraft 1.16.5
Forge 36.1.24
ImmersiveEngineering-1.16.5-5.0.0-135
ImmersivePetroleum-1.16.5.3.2.0-3
immersiveposts-1.16.5-4.0.0
jei-1.16.5-7.7.0.100
Crash log: https://pastebin.com/fqszkbbq

yeah I did not have a crash log, so thanks @SonicSpeedster16