Occlusion problem

I have been playing with lightmapping in unity but cant get around this particular problem with occlusion rings forming surrounding the objects. Any hints or settings i should be aware of?

I have tried this in both Unity Standard lightmapping and Lightmapping extended tool on asset store but in vain. artifact appears in both compressed & uncompressed lightmaps.

thanks.

olright, so this problem was solved by playing around with “contrast threshold” value from global illumination tab in Extended lightmap tool. I was using a default value, however, problem was taken care by setting the value of 0.01 in my case.