yeah it has to do with the fact that those spots are pure alpha compared to everything else and it tries to make a "bevel reflection" like effect
you can actually fix this when you make decals (everyone take note)
when you're done with your decal, add another layer above/below it that is a pure grey color, and it has 1% opacity. this will cause the entire side to be filled and will not try to find anything pure alpha to bevel on
I wish badspot would have done this before