I haven't spoken with Thule. I am still waiting, according to the dealer, for GM to decide how to proceed with the repair. Apparently, another truck in the area has had it happen too, according to the dealer.
I've never had the rack with more than 100 lbs on a dirt road and maybe a max of 150 lbs on pavement, all short distances. Body shop and I believe it is the cantilevered portion flexing the rack down to the bed rails. I don't think I would have had this problem if I was always on pavement. Thule only recommends lowering the carrying weight if you go off road and supposedly it holds 500 to 1000 lbs depending on what you read.
however, i just keep having bad luck with this truck as a load i was carrying damaged the front of the bed. how it happened is almost unbelievable. essentially as i was braking normal and coming down a hill when the truck violently downshifted causing light lock up of the rear and sending stuff flying / breaking my tie down straps. after that it was back to normal. i take ultimate responsibility for not securing the load properly but strange. no CEL, no abnormal stuff afterwards, just carrying about 3000lbs in the bed.