After many trial and error attempts to revert to NVIDIA v8.2.3, I succeeded.
This reset the system so I had to add sources again. When I tried adding Philo as a TV-Everywhere source, I was unsuccessful because Philo never sent the confirming link to the email address of my Philo account. When I called them, the support person said they could see my request but said Channels was sending them an invalid token.