Rear exterior ight
They must have some rookies on the line doing the wiring on those exterior lights. Mine does not short out, but the switch that is supposed to control that light controls the light in the closet instead. The outside light is not switched. The only way to turn it off is to disconnect the coach batteries, or take out the bulb, which is what the dealer did. In my case, I suspect the problem is in the wiring of the slide-out rather than in the control panel. Access to the wires will be a challenge.
Your problem is worse than mine. How do these things get out of the factory like this? Or, if they get out of the factory, how do they get through the dealership? They have this nice PDI form that pledges that they have checked everything, but it seems the only thing they have checked is the boxes next to each item that they were supposed to check.