The backup light switch is part of the NSS, so he may be on the right track, but I'd look for a bad ground somewhere in the backup light circuit. It might be in the wiring for the lights themselves. It's less likely to be in the switch than in the wiring. As I recall, the switch itself switches the ground circuit for the backup lights, so if anything at all happens when it is actuated, I'm pretty sure that it means the switch is working, but the circuit beyond it is bad. If the switch were not working, nothing at all would happen, and if it were shorted, it would simply leave the backup lights on all the time. A bad ground will cause the backup lights to seek ground through some other nearby circuit, such as the A/C compressor clutch, etc.
Edit: correction - I see from the 95 FSM that the backup light switch is on the hot side of the circuit, not the ground side. I still think that means that if it works at all it is not the switch that's at fault, but a bad ground somewhere else.