eraucontroller,
I have a '97 that is loaded with weird electrical do-dads, so I wouldn't be surprised if your '92 has some of the same! What I would check is the taillight assemblies themselves. They are probably plastic housings that require separate grounding which you might be achieving through the filaments of some of the other lamps which would make strange things happen.
I would take each side apart, verify the condition of each little bulb, replacing them if need be, and make sure all the ground wires are clean and secure.
If the plastic housings are bonded to the bed, the bed must be bonded to the frame. It's sort of a long shot, but it will take this question out of the equation. Good luck.
Stuart
