Both reverse lights in the rear bumper have stopped working. I still get the proper gear selection readout on the cluster (PRND321) it's just the lights that don't work. Bulbs are tested good - bad XYZ switch?

 

Do you have power at the bumper fog lights? Could be many other things. I'd start checking for power at that fixture and work my way back, checking each connector

 

I don't think XYZ switch because that would probably raise a whole lot of other problems as well.

 

One of mine would come and go. I found a bit of corrosion in the pins of each light assembly. I cleaned them best I could with some electrical spray cleaner and added a bit of bulb grease to each socket. Been fine for several years now. They get a lot of crap splashed up there even on the street.