Montana Rog -
Not sure if it was an epidemic, but there have been some Montana and Big Sky's that have had broken welds. Once they start, they get pretty destructive inside.
Symptoms are forward lower molding movement when the 5th is supported on the pin or hitch, as well as later symptoms that may include exterior cracks in the siding near the bedroom slide, or interior separation or compression in the bedroom.
To inspect, you need to remove the lower cover around the pin box. Inspect the frame welds and also the spot welds at the side frames that hold the aluminum walls as shown in this picture:
http://pic30.picturetrail.com/VOL152.../187810455.jpg
Also check your frame welds in the upper parts of the forward compartment and LP compartments as shown:
http://pic30.picturetrail.com/VOL152.../187810467.jpg
If you feel uncomfortable checking for the problem, I would take it to the Dealer.
There are several posts that show some of the broken welds. You can use the search feature.