Building Lighting freezes at 80%

Hi everyone

somehow the lightmap building freezes at 80% when I want to build one of my Projects.
The scene is jsut a basic renderingscene for some weapons. I only have one mesh, one directional light, one skylight and one spot light, one LightmassImportanceVolume and a selfmade skysphere blueprint in the scene.
I have checked my lightmap resolution, but it’s also at the default of 64. Other projects can build the lighting without any problems

Does anybody have a clou what can be wrong here?