Just had a similar problem. I installed a galvanic isolator during the spring prep period and it worked great, including at the dock after launch. Went for a short sail, came back, and the RP sounded every time I lit off the inverter. Dock-side sages said that blowing the isolator would do that. Took the isolator out of the circuit, no more alarm, will monitor zincs closely. Heard tell that there was a surge at the dock at some point, but it would have been over unless it occurred in the short time between plug-in and turn on. FWIW.
Bill Coxe, O40 Kukulcán, New London, CT