Solved Networking issue involving Verizon

I'm increasingly running into a networking issue involving new Verizon routers that I do not understand.

Let me explain my home setup first ...

I connect to the Verizon network through an ONT box on my basement wall. Connected to that is a Verizon WiFi 6 router -- a tall white box with a single white LED, on the front, and no model number I can find. That box is then connected to the coax network in my house through a coax cable.

Upstairs in mh home office, a companion Verizon white box is also connected to a coax cable. That box is then connected through cat-6 cable to my Linksys Ea8300 Wifi 5 tri-band router.

My home office devices then connect to the LAN ports on that Linksys router.

My other devices connect through WiFi to the same router -- using the single 2.4 band and two 5 bands.

I have an HP-AIO PC in my TV room that talks over 5GHz Wifi to my router and then to a Media-Server I have on the local network. I use this to stream video to the TV, which is connected via HDMI cable to the HP-AIO.

It has been this way for years, but with older Verizon equipment -- and without issues.

Then a few months ago, I started getting network dropouts. I contacted Verizon, told them about it, they said my old equipment was no longer supported and I would have to pay for new equipment (surprise! surprise!) -- so I did that. But the dropouts have continued.

As a test, I disconnected the Verizon router in the basement and plugged my router into the ONT and then ran a 50-foot cable to a network switch upstairs which then connected to the Media-Server box. I still got network dropouts. So, to me, that ruled out the Verizon routers as the source of the problem.

What confuses me is that when this happens, the streaming signal dops and I can see on the HP-AIO that the Internet has been lost.

OK -- but when I try to contact the Media Server via Wifi from the AIO, it can no longer see it. When this happens, I check my Linsys router upstairs and the network cable icon and Internet icon are both lit -- indicating no Internet signal is being received. That makes sense because the Verizon Internet connection has gone down.

But what is confusing -- why does losing the Internet from Verizon then make my locally networked devices no longer able to see each other? I don't see why losing the first should then make locally networked devices suddenly unreachable.

You have a lot going on in your setup so probably going to be difficult to troubleshoot in a forum...

What specifically loses network connectivity when the issue occurs? Everything, specific devices etc?

Also when you say I lose network connectivity, is that anything or specific protocols? Web (HTTP/HTTPS) have you tried ping and traceroute by both IP and DNS, arp caching, and does one work or neither?.

I would really suggest hand drawing out your whole network and identify choke points (routers, switches etc), when the issue happens then determine which devices have issues, what choke point do they have in common?

Also would help to have wireshark on a few devices and monitor that when the issue occurs to help narrow down which networking layer is the issue at.

In thinking about this further, I have realized that the common hardware in all the failures is my router. So, I have swapped that out for an old router that had no history of problems and will use that for a while to see if the dropouts continue. If they do not, then the new(ish) router is the issue and would need to be replaced.

UPDATE: I have since replaced my router with a newer Archer router -- and the problem has disappeared. So, it was apparently the router,

Will mark this a solved.