I have an old Rolleiflex Automat 3.5 which was working fine up until a few days ago. The shutter is acting strange... when I advance the film lever, it opens the shutter, sometimes firing it, sometimes leaving it half open. When I fire the shutter release after that it clicks, but no shutter action. When the shutter is jammed open, setting the shutter speed to 1/500 or extending the bellows all the way will close it. Any help?