Classy F

I have a Hot Spring 1992 classic F series. Everything seems to function fine except it trips the GFCI after about 30 minutes. It doesn’t matter if all features are turned on or all are turned off. It still trips about 30 minutes in. I had an electrician check out the circuit to the house and it seems fine. He didn’t want to touch the Jacuzzi though. I’ve called my local Hot Spring dealer but they don’t respond. Maybe these old tubs aren’t on their high priority list. Not sure what to do at this point. Any suggestions.?