That should be an auto-resetting breaker. There’s usually no issue with them, so if it’s faulty you’d have to check online or Beaver Coach parts for a source, or perhaps another member here can suggest one. But you can at least check with a voltmeter that voltage is making it from the breaker’s “hot” side to its mirror control side, helping to narrow down any other problem spot, or even simply a loose or corroded breaker nut.
Also check the tightness of all the screws on the ground bus bar(s) in that electrical bay, as your mirror wiring diagram shows a white ground wire (S16?) going there from the switch; most white wires in the bay have identifying printing on them if you want to try reading each, but that usually means snipping wire ties to loosen bundles and get any clear reading.
That said, if you’ve had the console panel off and been rummaging around under there, my first guess would be a disturbed wire or connector at the control switch. The diagram indicates that only the mirrors’ heaters require the ignition to be on, and are separate from the switch; their positioning motors are direct fed from the switch, breaker, and batteries (wire 108 to circuit breaker CB3). The diagram shows what appear to be some sort of connectors or coupler/plugs near the switch, for a black “hot” wire (BLK PWR) and a white ground one (WHT GND)… check those two connectors.
Joel
