My 1942 Leica IIIc has been acting up lately. The winding knob would jam tight. No way to advance further. To solve it: -I have to remove the film. -loosen the grub screw in the winding knob. -put a screw driver in the slot of the take-up spool stem and unscrew the winding knob slightly. -tighten the set screw and presto, camera works again. I'm thinking the knob is slipping slightly on the stem from wear and tear. It seems to work okay, except that the camera has developed an issue with frame spacing now. Some frames have more space between them, while about 3/4th of them are fine. Could be the stem is too loose now and the ratchet's not catching properly preventing the winding knob from slipping back a bit when winding. Will tighten it up a bit to see if that fixes the problem.