Hi! I have a vintage Pentax S3 that originally appeared to be suffering from 'sticky mirror syndrome'. However, on closer inspection I have found that the cause of this is that the shutter 'curtains' aren't quite completing their journey on the left hand side (looking down at the back of the camera). If I gently push it until it's completed it's journey the mirror then flips down. Does anybody have any idea if/how this can be fixed please?
I just got a H1a working that had the same problem. You'll need to open them up, clean out any gunk and lube the shutter curtain bushings with TINY amount of oil.