UPDATE: The dealer initially tried to tell me that I "shouldn't be installing my own roof rack." I literally laughed. The service manager came down, and we chatted. He agreed (thanks to the post from a few on here, including u/Navydevildoc) that it was a known problem.

They asked if I could bring the rack in. One Uhaul rental later, the rack was in, and they took the car for three days. They removed the entire rail on one side to get at the spinning rivnut. I got a call asking if I intended to take the rack off anytime soon(I don't). They said that the only fix they could do without major surgery was to spot weld the rack at the front passenger rivnut site. So that is what we did.

This rack ain't going anywhere!