A month later and disabling network discovery, Windows firewall and AV software to see if these were the
problem, I may finally have gotten to the bottom it it.

I set up a continuous ping to the router and to the DNS server.
The router had a good ping throughout the test,
the DNS server timed out a couple of times in an hour.

So that meant that the problem was most likely past my router
(though it could have been the WAN port)

So it was time to go back to the cable company.
The cable tech changed some connectors and got the signal strength up another db.

I tested it out after he left and it still had the problem.

I called support and they suggested replacing the modem.

I got a new modem and tested it for 4 hours with no problem.

I think this is it, but I'll wait a couple of more days to be more sure.