Copying the entire scene fixes it although i lose all textures all lights etc.
[/QUOTE]
Normally you shouldt lose any textures/lights, because you can select everything in the scene outliner -> how have you copied your stuff into a new scene? + which textures are missing?
I think this is the reason? Some times it tells me i need more memory… Is this fixable or do i just have to limit my scene to smaller projects?
[/QUOTE]
Either upgrade your PC, reduce the lightmap size, reduce the mesh count and make sure to place a lightmass importance volume