I have the same one in our 93 GBM Pursuit. It was getting slow to start but new plugs helped that.
We got a board for ours online.
Sounds like your thought on the switch may be on target. You might try getting some electrical contact cleaner and break and reconnect all the wires going to the generator board(s).
Our dash switch will not return to Center and will stay stuck ON if we are not careful. Typically I start it at the generator for test runs.
Seafoam finally stopped ours from loading up when we first got it. We adjusted the POT and got the no load voltage up to 128 volts and that helped stop the voltage sag. They seem to be great gensets.
Keep us posted.
