@Scoredo yes, it seems to be stable now. My internet connection has been up been up for 2 days. @CasaP Xfinity is another name for my cable provider (Comcast). And, yes, my topology is: Dumb Cable...
Just a quick update on this. I tried a few things that were suggested on other posting. I have switched the main P9 with one of the others. And also reset the Comcast modem/router. I will see how...