I'm not a manual battery expert, and it's really a shame that people push the manual
batteries, and then never show up to help the people in trouble.
I can tell you of one of my experiences. My brother in law has my old kiss box with the manual switch attachment. It started to act up, and finally, didn't work at all. We figured we had nothing to loose, so we soaked in in grain alcohol for about 24 hours, blew it out with canned air, let it set for a few hours, and the thing is working like new.
This switch had no battery connected to it, so I don't know the effects of soaking it with the battery. But as a last resort?? Try it at your own risk.
jd