Cannot use some websites without rebooting Arris modem/router combo (DNS_PROBE_FINISHED_NXDOMAIN)
We are currently having a very strange, somewhat frustrating issue on our Xfinity home WiFi network. All throughout the last few days (1-30-2020 to 2-1-2020) we will slowly lose the ability to connect to certain and seemingly unrelated websites. It will usually start with Google, which when connecting to it will give the error "DNS_PROBE_FINISHED_NXDOMAIN". Soon we won't be able to see YouTube thumbnails or comments. Then the videos won't even buffer. Eventually that gives a "No Internet" error. Sites like imgur and Reddit are available for a long time but cannot be loaded after enough time. Rebooting our Arris modem/router will fix this but only for a limited time. Four hours or so is all it takes to return to our "no internet" issues. We can live with this but, surely, rebooting our modem four or five times a day is not a true solution.
Before I get to attempted solutions let me list some information about our network.
*Performance Pro+ Internet Package (175 Mbps Downloads)
*Arris Surfboard SBG7400AC2 (router & modem)
* DHCP enabled for both IPV4 and IPV6
* 2.4 GHz & 5 GHz enabled
* DNS Override Enabled (Primary: 188.8.131.52, Secondary: 184.108.40.206, Tertiary: 220.127.116.11|Similar IPs for IPV6)
All but one device, a Windows PC, use Chrome for their web browser. Android Phones and Windows PCs alike encounter the same issues. Both Firefox and Chrome have the exact same results.
Three PCs use the Origin, Steam, and Uplay web clients for games. Every client will eventually report that they are offline and cannot download games or display web pages.
So far I have rebooted the gateway through both the built-in user interface and the Xfinity website. I have disabled DNS override, changed the DNS IPs to be Google's 18.104.22.168/22.214.171.124, and manually changed them to Xfinity's own 126.96.36.199 / 188.8.131.52. And finally, with few ideas left, I tried pulling the power plug and waiting five minutes in the hopes that the device just needed a moment to cool down and a hard reboot.
DNS changes have no effect. Reboots all have the same result. We are able to access all websites without any issues for a few hours before we slowly, one by one, lose access to certain websites. It is very strange to lose Google while researching the issue but still being able to use DuckDuckGo to continue the research. As I type I have lost access to even that yet am able to use any Xfinity sites. I'll be contacting Xfinity support Monday but I was hoping to get these issues fixed before then.