This seems to be the opposite of the most common spotmatic problem where the meter won't switch off after an exposure. I couldn't find anything searching these forums. I was given a used SP1000 about five years ago and it has worked wonderfully since I got it, but lately the meter switch ("SW" switch) has not been "clicking" into place and staying up when I push it. At first it would stay if I held it in place for a moment or sometimes pushed it towards the camera body while I pushed it up, but now it won't stay up no matter what I do. The meter still works fine, but the switch won't stay. Is there any way to fix this short of something possibly destructive that should be left to a professional?
You have to remove the front panel to get to the locking mechanism, located on the side of the mirror box. When you have the front panel off, be sure the screw holding switch knob on is secure--be careful-- some had plastic knobs and easily cracked and then you in deep trouble.