Recovering non-responsive buttons on 42S

[mats]

This is probably a naive and common question so I apologize in advance for my first post on this forum. Is there simple way to revive "non-working" HP calculator buttons using spray-on contact cleaner without taking the calculator apart?

I have an old 42S on which the "On" (EXIT) key stopped working along with the entire right side +, -, X, / and < keys. Figuring I had nothing to lose I sprayed the whole keyboard with CRC QD Contact Cleaner - basically soaked it. This more or less succeeded and I was very happy for about half an hour - but then the keys stopped working again.

Is there any possible merit to this approach? Has anyone else tried this or any other type of solvent? It seems tantalizingly simple and almost works, but of course almost isn't good enough.