I finally found a way to fix it! https://forums.unrealengine.com/t/lighting-not-building-swarm-seems-to-be-the-cause/311775/25?u=casper_ap
Thanks to domoskan for the fix:
- Windows+X => Command Promt(Admin)
- cd \windows\system32\wbem
- mofcomp cimwin32.mof
- Restart unreal engine (just to be sure)