We've had our Montana for 3 years now. Within 2 weeks after we got it brand new, parked at home, the camper was invaded with stink bugs. For the next year they continued to pop out, even in the Winter when the heat was turned on.
By the second year of ownership, the stink bugs persisted and we got invaded again. This time, I took drastic action.
I picked up a package of Raid bug bombs from Dollar General and set all 4 off in the camper. Of course, all food items, dog bowls, water bowls, dishes, everything... was all put away.
For the next couple days stink bugs were found everywhere dead. 10 days later, I repeated again. (by the way, slides were "out" when I did this.
For the next 6 months we continued to find dead stink bugs in some of the most unusual places, but no live ones.
The following Fall, I repeated the process again ... 4 bombs, twice, 10 days apart. And we've never had "live" stink bugs again.
I think the bug spray poison permeated every crack and cranny in the camper. I also turned both air conditioners on "fan" when the bombs were set off, and the second time the bombs were set off I turned on the furnace so the bug spray would get up in the ceiling vents and vents under the floor, and if there were any cracks or leaks, the bug spray would also get up in the roof between the rafters and under the floor.
To this day, we've not had any living stink bugs, but we do occasionally find a dead one.
When I posted this a couple years ago on some of these RV related forums, I got blasted by comments like ... be careful so you won't blow up your trailer .. bla, bla, bla. That's BS.
The bug bombs worked. After setting them off, we wiped down the counter tops, washed all the dishes again and washed the bed linens. And, we've not had any problems since. I think the poison in the ceiling and under the floor is still working.
By the way, I did open the back wall of front pass-through and set one off in that open space too.
So, my suggestion is, get some bug bombs and set them off in your camper. Go away for a couple hours and when you return get the vacuum sweeper out!