Ok, I emailed cox.help@cox.com just now. I hope they call to set up an appointment tomorrow. The problem is persisting.
I set up an appointment, and ... surprise! ... the tech found all the wires were fine and blamed my new modem I purchased in April (Netgear C7800, one of the ones listed as your preferred model for this level of internet service). The tech will happily let me rent a Cox panoramic wifi modem for $10/mo, while the device I paid over $300 for earlier this year collects dust. I am not happy.
I am now reading the tech support forum for the modem and they ... surprise! ... blame the internet service providers. The modem is apparently sensitive to the signal strength from internet providers. Is there a way to determine what the signal strength is for my house? This post suggests upstream 45-48 and downstream -7 - +7. The further from these suggested levels and the modem locks up - exactly what I'm seeing on my diagnostics.
See: https://community.netgear.com/t5/Cable-Modems-Routers/c7800-disconnecting-often/m-p/1948376#
I would like Cox to set my signal strength to work with the modem that Cox recommended for purchase. How do I make this happen?
The tech lent me a Cox panoramic modem as a test device, to show there was no issue with the line. My guess is that the panoramic modem functions well at a greater range of signal strengths. I am having no issues with its performance.
Are you able to see the signal strengths to my house? Are they within the range recommended by Netgear for the C7800? I can reconnect the C7800 if you need it to be connected to test its reception.
