R6250 Router dropping Internet access since V1.0.4.26_10.1.23 firmware update

For the life of me I could not type a m,essage body in the original post - but I can in a reply? Weird.

Anyway - since Firmware Update V1.0.4.26_10.1.23 I have had all sorts of hell with the router dropping Internet Access. I even read up some threads here about it which seemed to be inconclusive, but recommended both doing a factory reset & re-entering all configuration data (done) and reporting back here whether that fixed the issue or not (doing it) and also starting a new thread to avoid confusion. Well, I don't know if it will avoid confusion, but this is a new thread!

Restoring to "Factory Settings" and then re-inputting ALL of my settings - including reserved IP addresses and so on and so forth took a lot of effort and initially looked promising, but in the long run proved to be inaffective. My Android devices, my Windows 10 devices, hell anything I attach agrees that the WiFi is working, the wired networking is working, but DNS... ahh, therein lies the rub. Something about DNS is not happy which causes these devices to loose access to the rest of the world.

I have a teenage son. As a result I'm using the Parental Controls aspect of this router to try and reduce the number of dodgy sites he can reach. I have found that the only way to make my R2650 with V1.0.4.26_10.1.23 firmware stable is to turn off the forced DNS servers that are a requirement for the Parentl Controls to work and use the network/ISP-supplied DNS servers instead. That makes the router route, although at reduced security.