Lightmap UVs change after Bake

Hello, This is driving me crazy and cause a lot of problems to me. I try to bake nice Lightmaps since many days without luck. Now I figured out that the UVs are getting shiffted after I bake Light.
I setup my UVs very carefully and snapped the UV islands to a 64 Grid in order to prevent shadowbleeding. But when I hit bake the Uvs dont match up anymore. The get shifted slightly. Thats causing Shadow bleeding because the UVs are not snapping to the Lightmap resolution grid anymore. Here are two images before and after baking.
Can anybody help me with this? What could cause this?