Black spots in lightmap?

I have a mesh that for some reason higher then 64 lightmap resolution causes some weird black spots.

I made a testmap that has only one light and 3 copies of the mesh, I overrode the ligmap for each one and you can see on the “target” there is a black spot… which gets larger with higher resolution

Try setting lightmap resolution to a power of 2, e.g. 128 instead of 72 or 80. Also, try baking lighting as production. The preview lighting has always been terribly inaccurate for me.