Change out that switch to a new micro switch. It's either been bent over the years to make it work or the actual switch button is getting gummy/sticky. If you wiggle the machine and it registers sounds like it's sticky as it should be past the switch already and closing the optos, which you say are working fine.

And if that was my who dunnit it got blasted at pin a go go so many years it's probably due for a replacement switch haha.

Just thought of another thing. Look for cracked solder joints at the optos and switch. If it's a wiggle and it fixes it, then something is loose, gummy, or misaligned.