I just bought a M 50mm f1.4 and thought it was in pretty good shape. However, when I focus the lens, the ring shifts or slips and a very light sound happens at that moment. The slip occurs only once in a given direction and usually near the start of focussing. If I stop and go back in the opposite direction, it usually slips again. The lens seems to be operating fine, but I just want to know if anyone has had a similar experience. Is this indicative of some problem?
Jim
