Intermittent connectivity - especially VPN and VOIP sessions for work (Dynamic Range window violations and T3 timeouts

In May this year, I upgraded from the preferred 150 to Ultimate (500). I at the same time purchased a brand new Netgear CM1100 modem and Netgear Nighthawk RAX45 router. Immediately after upgrading the modem and using the new service, I started having intermittent connectivity throughout the day. It is more apparent when connected to my work VPN and during VOIP and video conference calls. During the day, my work computer is the only device using up any real bandwidth and is connected ethernet and 5g wifi to my router. Other devices "connected" include my phone, ring camera, chimes, and doorbell, and a docked tablet with Alexa show mode. I had a service call and they checked and tested my connection, cleaned off the fittings at my house(DMARC) and the pedestal across the street. Speed tests came back all good and so they said it was fine. My issue is not with speed as it regularly runs 480-515 when tested. My issue was at one point escalated to a line tech of some kind and I was asked to email in my modem connection and logs. I did so and for a few days, all seemed fine. I was then told:

"Welp, as long as those correctable and uncorrectable codewords aren’t exceeding 1% (which they don’t look like they are) you sir are rockin.
Thank you for the reply; if you would like for me to pull up any information, feel free to reach out."

4-days later I noticed the issue returning and emailed back the logs showing multiple  "DHCP RENEW WARNING"s which I e-mailed with no response.

From there it got worse and in June I began seeing these items multiple times throughout the day each day and has continued intermittently for months:

Here's my current log. Unfortunately the log is capped and doesn't keep all history or have an auto email or output so I can capture everything:

Here's my current status:

Some more info about my setup. I have one line that was run by the installer from the DMARC into my attic. From there, the line used to run down into my living room. That was cut, new F Compression Connector installed in the attic with a barrel connector to a new line and that is run into my office to a wall plate with a barrel connector (from the installer). From the wall plate is a 90º fitting and a <4-foot coax line to the modem. I am not sure about the line from the DMARC to my attic, but from there is all RG6 with F Compression Connectors I bought from a contractor cable installer. This is how the setup was tested in May and hasn't changed. I swapped out the 90º connector at the wall plate in case that was bad (I have used multiple of these on TVs and wall plates where I have run Antenna lines through the house and had 1 fail (tested with a Klein Tools Coax Explorer 2). 

Can anyone shed some light on what the issue can be and how I can get COX to fix this even though my speeds are good and the uncorrected codewords are less than 1%? The intermittent connection especially when hosting work meetings with our client is very disruptive.