I never posted the resolution to this problem. Airstream worked with Bob Jones RV in Houston to get the replacement done. It took a long time but didn't inconvenience me much, since we could use the van in the interim. The bolt failure looked scary but the sofa went up and down with no hitch.
We also got the failed sun screen motor replaced.
I had to pay out of pocket for the RV shop hours, but then Airstream sent me a reimbursement by check. So all is OK now.
Leigh & Bettie
2017 Interstate GT