I have a 2018 Bighorn Traveler 39MB. Not the Montana but, I could certainly live in it. All of my issues have been assembly quality issues. The materials like floors, cabinets fixtures and structure have all been fine since September of 2017 when I bought it. No issues with plumbing, (except the lack of drain seals in the shower, again assembly issue) electrical, or gas, appliances, slides, fixtures have all been good. As with anything, constant maintenance is key.
Good luck on the search. Hope it is helpful......
2018 Ram 3500 Crew Cab Laramie 6.7L, Aisin, air ride, Ram puck prep, SuperGlide 20K auto slide.
2018 Bighorn Traveler 4 slide w/Apt.
It’s not what you’ve done that commands respect, it’s what you do.
Happy Campin’