2007 T800 Kw tail light back feed

[Waterloo]

I wonder, I had a Pete that went bonkers on my electrically. Spent days trying to figure it out and finally had to take it to a shop. It took them a few hours, but they discovered it was the grounding step from the fifth wheel to the frame. It is a braided stainless steel strap. Somehow it broke at the connection. It was there, but only held together with a few strands of stainless wire. Maybe see if that strap is intact, if you have one.