This is actually my 4 router with the same problem.

I have spent days and tons of hours on support. After I install a new router everything is fine until the next morning. Connections drop on every device in the house, from PCs, iPads, iPhones to Rokus. Sometimes only one channel drops. It last until you power off the Spectrum modem and AX6600 & reconnect devices. One tech stated I had a duplicate IP address and it was a network issue and not the router. ???  The router IS the network, no?  I have a Spectrum modem(no wifi), router, and devices. I also noticed that I am having to authenticate myself almost every time, like with Amazon and not like when I use to just login. Here is the latest log from the AX6600.  Any help would be great!  Thanks!