On reflection, of course I'll get the camera repaired! There is nothing anyone can say or do that will get the camera working by, say, tomorrow night. And any likely repair, even though it involves shipping overseas, will be much cheaper than even the cheapest new camera. The suggestion to replace cables is interesting. I have a spare USB cable that I can try. Since the problem shows up in biases, I don't need a dark sky to test it. What's particularly frustrating to me is that I broke my right leg last July 2, and it's only been since mid-December that I've even been able to enter the observatory. Now that I finally have a clear, dry night with decent seeing, my trusty camera goes south.
The comment about QHY vs ZWO is interesting. Mike Barber, formerly of SBIG (I think he was a founder), was working for QHY at AIC 2019. I would think he has some confidence in the product to be willing to hitch his star to QHY.