Lightmass Crashed

Hi guys,

I’m desperate, I have this lightmass crashed in the message log every time i Build and I don’t know how to fix it. I have made a new scene, I have changed the sphere reflection, I have reimported the mesh again and nothing has worked. I have searched the internet and there is no solution. I am quite a newbie to unreal and I can’t find the fault I hope someone can help me. Thank you very much in advance.