RAX35 device login refused

It seemed I achieved some stability with this device after installing older firmware and stopping short of newest. Occasionally have quirky issues with connection which remain unexplained. But after a few months of working smoothly with one TV it suddenly refused allowed logging into WiFi. I tried many ways short of rebooting the router which I eventually did and that worked.

What is wrong that these routers are so problem prone? If it is not reliable dare I trust it for security?

What is wrong with Netgear that they build so many products but few seem reliable?