OK, turns out one of your suggestions was right on. I had amber 1156 bulbs in the front. Changed them to clear 1157 and they work fine now. Except now...
With headlight switch on off position, doors closed and courtesy lights off, the rear tail lights and arrows are on, and brightness adjustable via the headlight switch!
The 1156 were single filament bulbs. That was the source of the problem. The only place our cars use 1156 is in the backup lamps. Scroll down to find the correct bulbs. Be sure the tail lamps also have 1157s.
