I'm wondering if someone can do me a favour? If you have a working rb67 120 back, can you open it up, and look at the rollers on the exterior casing, the ones that keep the film against the pressure plate. Please tell me if they are relatively flat against the exterior casing wall, or if they are extended up away from it. On my back one of the rollers is slightly elevated from the casing. I wonder if this could somehow be causing the scratching, having a roller edge dig in to the film slightly?