My Challenger GT is a 2014 chassis and 2015 coach. I have the exact same issue. We have only had it for a year, plus we live in SW Florida so it isn't high on my priority list yet of things to correct.
I am wondering if the bedroom vents were completely closed off, would that force more air up to the front floor vents in the coach? I'm not a HVAC guy so I'm not sure if that sort of modification would trip some type of sensor and shut the furnace down or what.
Full Time in 2017 Newmar Ventana 4369
pulling a 24' enclosed (Mini Cooper/Harley/Kayak)
(traded 2014 Thor Challenger)
US Army 70-73 Retired LEO