I just bought a Spotmatic SP and a Super Takumar 55mm 1.8 at a flea market for $40. The camera is in fantastic condition and appears to work flawlessly, except for one thing: the little plate at the bottom that pushes in the pin to stop the lens down for metering doesn't return automatically. I can push it back manually, and it's stiff when I do that. Sometimes it works, but most of the time the camera stays stopped down after I push the metering button. Is this a common problem with Spotmatics? Is there any way I can fix it, and if not, would a CLA be likely to fix it?