Why wouldn't you want ac in the bathroom?
Check the duct is sealed to the vent. Could be leaking into the ceiling. Especially with the AC vent closed could push even more into the ceiling.
2017 Eagle 293RKDS, factory ordered, lots of mods and upgrades. More than I can list.
2018 Ram 3500 crew cab long bed SRW diesel 6spd Aisin 4wd Tradesman.
B&W Ram puck 5th wheel
Mopar wheel to wheel steps