I just got a 501c/m and the camera and back are in great shape. However I've ran three rolls of 120 through the A12 back and each one of them has had dents and bumps in the film. First two rolls I chalked up to being new to putting the rolls on plastic reels. Third roll I had my Darkroom instructor load the film onto a steel roll for me and I ended up with the same results. The bumps and dents are all over the film so not sure I can narrow whats causing it. Any ideas? It doesn't show in my prints unless its supposed to be really flat then you get the light from the indention bent. Thanks -Twellsphoto