My F3 was giving me fits - lot's of scratches on the base side of the film. I checked the pressure plate and everything looked OK. I got the bright idea to take a (factory loaded) roll and waste it by running it through, then just fixing the film and checking it with a magnifier. Sure enough, there was a slight burr that I couldn't feel (my hands aren't exactly soft) but was scratching the film once the pressure plate was doing its job. I solved the problem by buying an MF-18 databack - which I wanted anyway!