I don't think the film was fogged while loading - The dark area is virtually identical (depth and angle) on all 4 frames. The bellows aren't sagging (although the angle seems to match the shape of the bellows). There's nothing inside the camera. I'm wondering if there's some sort of reflection or strange light behavior going on inside the lens - it's the lens I asked about in this post. It's "press fit" into a black ABS plastic lensboard, threads out, and around 1/2" of lens back into the cavity - having said that, I just looked at the part of the lens inside the body - I wrapped black electrical tape around the first 1/4" or so but the rear edge is reasonably shiny brass. I see more electrical tape and another test in my future. I had tape sealed the hole in the underside of the lens body and saw no light leaks around the aperture, by the way.