I tried to trace the big black wire by drivers seat back because I figured, given it's size, it's likely the charge cable coming forward from converter. When I got back to wiring harness around the charge controller and under-bed 110v / 12v fuse blocks, I lost it. I just couldn't figure out how 13.3 was heading to front of couch, as it was clearly heading into the 12v fuse panel under the bed... but where was it going from there?
So I took apart the back panel and began to inspect things, when... I found a melting part of the back of the 110 section of breakers...
I immediately disconnected shore power. Went back to disassemble.
It was warm to the touch (the plastic). Oh, shit...