(Drakador_Chaos) Kroom
So it seems to have been differing versions of the mod, maybe due some number behind the name placed by some folder duplicate, seems to work now.
EDIT: Turned other mods back on (huge ships, WH40K and armor expanded) and now it´s incompatible again.
EDIT(2): After some testing it turned out that in multiplayer you can only use either forge or armor expanded, for whatever reason, even though in singleplayer it is working perfectly fine together, maybe some issue about the naming, though I have no actual clues.