Apparent Issue with Polaroid Back

Hi all,

I have the camera and Polaroid back mentioned. Should both the rollers on the back's business end move freely? On mine, one does, one doesn't. After pretty thorough cleaning I got a lot of crap out of the rollers, but the bottom roller (closest to the camera body) seems stiff. Consequently, when I load pack film and pull the dark slide from the pack to expose the first frame, the paper rips off. That seems wrong.:

Any cleaning or repair suggestions, or should I just find another back?

Thanks!

Kurt