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Cox Internet service (no phone or television) worked fine for years (basically no outages) with Netgear Nighthawk X4.
Switched to phone and Panoramic wifi .... now constant outages and errors.
Now on my third piece of hardware.
Result: Cannot connect 2 Google minis for weeks.
Worked fine with Netgear.
FYI: Using Panoramic modem in a small space under 2K feet
Why did you get a modem/router gateway when you had your own router? I would suggest separating the phone modem from the interenet modem and then use your own Google routers/APs. Cox will provide the phone modem for free and all you would need to buy is a stand alone internet modem.