I think he means that the flippers are not controlled via software and transistors like they are with fliptronics. Gottlieb System 3 flippers are still pretty archaic. Power is sent from a relay that’s powered up on game start, and electrically is routed pretty much the same way as they were back in the EM days.

I think the first obvious place to look is at the flipper buttons on the side of the cabinet. Make sure the contacts aren’t stuck closed, or that a solder splash isn’t making a dead short.