As it turns out, Whirlpool knew about this problem, implemented a fix approximately the time my unit was built, but never issued a bulletin. The repair part is 9760862. My oven was supposed to have this already, but possibly the first "fixes" were not completely effective. The power fail would also occur at the completion of the regular oven cool down cycle. A symptom of the failure is that the clock would reset to 12:00. A real power failure caused by tripping the breaker would cause the clock to come back up near the time it lost power. I have the new part to fix my oven, but it is not installed yet, so I will keep my fingers crossed.