My son is using an RB67 for college photo projects and has encountered a curious problem with his backs. Black and white film (Ilford) will correctly trigger the frame counter on the back, but color film (Fuji) will not. Once the first frame has been shot (he has to pull the darkslide while winding on to see film so that he can line it up, sacrificing the first frame), the film will advance and stop correctly, but no counter. This happens with both of his backs. I can only guess it has something to do with the thickness of the backing paper. Has anyone encountered this problem, or have a solution? If it is a mechanical problem, can anyone suggest a good repair resource in the Midwest (Chicago)? I haven't seen the camera myself, and I'm more of a Hassy user, no experience with Mamiyas.