Hello;
I do not own a pro model but have the earlier 1000s (non removeable back). Last year I had issues with the film advancing. Tracked this down to the film inserts. Had to replace the rubber tire that rides on the film backing paper. The old tires were hard and had flat spots not allowing the proper spacing for the film advance to work. Now I load up the film before shooting to avoid these flat spots on the tire. Hope this helps, Steven.