IT'S FINALLY SOLVED! :)
"The consensus is that the manufacturer added a power wire to the thermostat, that is unnecessary and is causing a power loop back through the ceiling lights."
After everything they've torn apart to find the culprit, this was the issue. I'm glad we finally found the fix and now they can remove this extra wire and put trailer back together. I'm wondering :h if other R-vision trailers have same issue that were built around this timeframe (Jan/Feb 2014)?
Anyways - thanks all for your contributions and ideas! I'll keep you posted if anything else changes.
