RE the two suggestions that I was over the tongue weight rating...
Kia rates the 2016 Sorrento with a 350LB tongue weight limit.
The 2003 Starcraft 2406 has a dry tongue weight rating of 180LB. I don't see how I could have added 170LBS to the tongue if I tried. Meanwhile, since I used electric sites (used an electric space heater instead of the furnace), didn't use the shower (didn't bother with the water heater), and used a Coleman camp stove (didn't use the camper's stove), I never filled the one 20# LP tank.
So, I'm glad you are trying to figure out why there may have been a problem, but that is not the answer. The only one I can think of, considering I never abused it on the road in any way (no off roading, heck it is FWD, I try my best to avoid pot holes, and I'm going on 48 so I'm a pretty conservative driver these days), is a manufacturer's defect. If it is from towing, then Kia over-rates their vehicles. It might be a sign that the trucks and not CUVs for towing folks may be correct, and I will be going with a truck (with its more substantial suspension) next time.