Device: Netgear R6220 Firmware: 20.02 snapshot r18400-f9782f5bcd

After the router has been up a while it will start to lose wan connectivity to my ISP (Frontier FiOS). I'm unable to ping the default gateway. Using my cellular data, I ssh to a remote server and ping the same gateway and it pings fine.

It's only down for a a few to 30 seconds and comes backup usually with the following message

Dec 30 01:07:02 gateway dnsmasq[304]: possible DNS-rebind attack detected: dns.msftncsi.com

There is no indication that the wan connection is down, and the lights don't change.

The ISP sent me a new router which I have now connected up and it's been stable.

I've tried two different R6220 routers, since I have a spare, and that gave the same issues.