ISP vs eero
ISP connection is sporadic. It would be helpful to see a connection log within eero so I can provide specifics to the ISP. I called eero support and was told they are not available to users.
As a workaround, you can run 2 simultaneous cmd windows with a ping test. Window 1: ping 188.8.131.52 -t and window 2: ping 192.168.x.1 -t
Run it for 5-30min then hit control-C to cancel on both. It will show you the packet loss for your Internet connection (ISP) and the other from your router.
You should always have 0% packet loss from your router to your PC.
Screenshot that and show it your ISP for proof. It helps.