Bent Rear Axle on 2009 Montana

[gat1]

Does anyone know if it is possible to bend a trailer axle by lifting (jacking up) a trailer in the wrong place? This spring, I had my 2009 Montana into our RV dealer to have them repack the wheel bearings. Last week when I was putting air in the spare tire I noticed both tires on the rear axle were worn down to the belts on the inside. The door side was much worse than the other side. It was worn about 3" wide (both ware spots were on the inside) and the belts were totally exposed. The tires (Firestone Thunderer St 235/80 R16) have less than 5000 miles on them. They only had about 200 miles since repacking the wheel bearings. Since the repacking of the bearings I have not hit any potholes or curbs. Service manager said it could be cause by backing up into too tight of a turn. (same turn I've been making into our driveway for some 7 years).
They claim the axle is bent.
Nothing else has changed since getting the trailer in 2009, same vehicle pulling it. Seems funny all of a sudden the tires are wearing. I appreciate any comments, suggestions.

Also, any comments on the tires? I was reading about the Firestone TransForce tires, are they better than the Thunderer??
Thank-you, Gary