In that case it's starting to sound suspiciously like the filter combo

I don't think you will find any particular angle that you can set the VND filter
to eliminate this. It sounds like there's a bit of polarised light getting through
the whole combo. My nearest experience is the various colours you see when
driving with polarised sunnies and looking at scenery through window tinting.
The tinting already polarises some of the light from outside, and the glasses
then... cause the illusion...