vray clipper and vray dirt issue

Hi guys i have this very odd problem that I've been facing with Vray clipper and vray dirt. This is a simple test setup I have here, by using vray clipper mesh to clip cube A. In my clipper settings I excluded cube B. however in my vray dirt render, the clipped surfaces of the cubes gets rendered out black. Even cube B, which should be excluded by the clipper got affected as well. Not sure if this is a known limitation with regards to vray clipper and vray dirt. Wondering if anybody have a solution to this problem? Been going around looking for solutions but I couldn't really find any. ><

Im using Maya 2016, vray demo ver. 3.4
In my setup I'm only using a domelight, with no GI.

simple setup

beauty render

vray dirt render