I recently bought an MD 35 f/2.8. I tested it as soon as it arrived and everything was fine (optically, mechanically). If there was something I could report was just that the aperture ring didn't have that positive click into place but it didn't seem to affect anything. I mounted it on an adapter and noticed that it was a bit stiff to lock into place. After a few days, the aperture ring doesn't work anymore Its stuck at the widest setting and doesn't move. At first I thought it was a problem with the adapter so I tried all my other adapters but still the same (all from the same seller and all work great on all my other MD lenses) Any ideas?