I just got this very clean Pentax S3 and it has a problem. When I put the lens on A the aperture is supposed to stop down to the set aperture before exposure but I found that sometimes it only stops down partly or not at all. The problem is worse if the camera is pointed upward (lens pointing up). The problem is not so much if the lens is pointed downward. At long exposure like 1 sec I could see that the aperture would stop down slowly to the set aperture. The aperture stop down pin on the lens actin feel normal. It doesn't feel tight so I don't think it's the lens. When pointing the camera upward sometimes it gets so bad that the camera could not complete the cycle. I would greatly appreciate and help on this matter.