Predictably intermittent...

Battery disconnect makes it work right for a while, then problem reappears. Like I said, electrical is NOT my bag, but that's kind of why I was thinking it was something physical like a relay or diode. When the circuit goes cold it resets. Then once it heats up, bing, she's locked on.

Maybe, just for grins, I will disconnect/reconnect the battery and check the readings for the GRY/BLK "Courtesy Light Control Output" wire.