Mine does that too. I had a test with a dummy film and the back off, winding and rewinding. It's actually the film itself rubbing on the take up spool's flanges. Because the take up and the sprocket drive rotate in different directions, there's a fair bit of tension on the bit of film between them. Under load the take up spool is pulled out of parallel with the film plane. The bottom end of it moves towards the back of the camera. The whole take up is quite floppy, in that you can push the bottom end out of parallel, forward and back, with your finger. I wouldn't worry about it, even though it does sound disconcerting. It's just Soviet build quality!