Thank you for the detailed explanation. I removed the "Avast Online Security" extension, power cycled my PC, and re-added it, just to see if this might solve the problem before I did the "Repair" step to the Avast program, since there was a chance that settings might change.
It's been less than 24 hours, but so far, so good. It hasn't stayed enabled this long since the problem started, so I'm hopeful this was enough to provide the solution. I'll know more in a day or two.
Thanks again for the lead. Without your help, I wouldn't have thought about removing and re-adding the extension.