can anybody help me what causes this unkown light and shadows ins
ide?
it could be un-welded vertices at the corner - check in your modeling package.
or light map UVs of a wall receiving light are too close to light map UVs of a dark shadowed wall - in which case the light pixels from the lit wall are bleeding into the dark one. This happens a lot with low lightmap resolutions. Try increasing the default light map resolution in the static mesh editor.
it seems not to be working, i try increasing it to 1024 even 2048 but nothing happens 