[KJinDC]

It's difficult for me to explain since I'm so non-technical. Here's my attempt though.
The tail light assembly contains 5 bulbs. There's one small bulb that on the outside edge for the running lights, one yellow bulb for turn signal, and three additional bulbs for the brake light, reverse light, and additional running lights i assume. Two of those three bulbs are 1156s meaning they have a single contact point at their base through which they are powered. The bulb furthest to the inside is an 1157 which has 2 contact points. One of the two contact points in the assembly, not the bulb, had broken off and was trapped in the housing the bulb screws into. On the track, this tiny piece of metal would fly around and contact something within the housing thereby shorting the line. On the street the flake of metal would mostly lay dormant in he housing since it wasn't really exposed to the braking or lateral Gs we see on the track.
I only found this piece as I replacing the bulbs (again) so that I would be sure to have new bulbs when I took the car to the dealer to trace the electrical issue. Does that make sense?

Tony, I realized I forgot to thank you, Dr. K, John Sullivan and Joe Lagoia for helping chase this bizarre issue down over the course of the weekend. I'm glad it's resolved (cheaply)!