So it turned out that my IPD adjustable cam gear was badly worn, which allowed the timing belt to slip. I contacted IPD by e-mail, and before I could even send them photos they had shipped a replacement gear to me. They had become aware of the problem before me and have made some changes to eliminate the wear. They did request that I ship them the failed gear once I have the replacement, which is a reasonable request.

I suppose I could rant about how terrible it was for an expensive component to fail prematurely, but I do flog the car and they impressed me with their rapid response (overnight) and no-quibble attitude. I don't buy routine parts from them, but their customer service will keep me coming back to them for the specialty stuff whenever I need it.