Alright, so I've shot a few rolls and it appears to be working 100%. Got a new FD 50mm 1.4 and it's great. I've only seen the results from the third, fourth and fifth rolls as I didn't have access to colour developing until now, which is where I shot the first two rolls including the exposure tests, but I don't see any exposure issues on the rolls I have developed (all of which were taken relying on the built-in meter by the way—seems to be very reliable). Thing is, I was shooting the sixth roll and as I was done with it I started winding it back into the canister, and it felt too loose. Thought something had become loose so I opened it in a dark room, and I only saw the canister, so obviously all film was inside it. My guess is I could only do one or two spins before it was completely inside it, meaning I exposed the same two or three frames constantly, effectively losing all photos I took. Since I wasn't sure about that and had no way of taking the film out of it (or, obviously, to see any picture without developing at least part of the roll), I loaded another roll I had on me. Paid attention a couple times to see if the rewind knob was spinning every time I advanced the film, which it was, and then stopped worrying. A day later, I pay attention again, and it didn't turn. Not knowing whether I had already exposed that frame, I covered the lens, snapped a photo, and advanced it. No turn again. I did it twice more, and it did turn both times. I opened the back of the camera and the sporckets were correctly lined up. Fine. Today I took a photo, it didn't turn. Covered the lens, advanced, and it turned. What could possibly be the issue here? I don't feel any looseness when advancing the film.