Hey Steve –
I have this exact problem. I was wondering if you ever found a solution, or if this is just how the Fader ND is. I have a Canon 60D and a 35mm zeiss lens. This is a sample indoors
https://www.youtube.com/watch?v=lJKm5QZ16ag&hd=1
In addition, I get reflection even when not shooting near windows. For example, shooting parts of my house outdoors. I emailed light craft, but did not get a response. This happens to me across the entire ISO range. I saw your post and was wondering what ever came of your experience. Very frustrating.
Thanks,
Matt