Completely unreliable connection

Like many people have posted, I'm seeing frequent and somewhat random connection drops and errors in the modem event logs. This has been occuring for months now, mostly occuring as severe degreadations in performance but occasionally increasing in severity to full dropouts of service.

I've followed the troubleshooting steps here: https://forums.xfinity.com/t5/Your-Home-Network/Internet-Troubleshooting-Tips/m-p/3310447#M316652

• There's no splitters in the system that I have access to.
• I recently replaced the coax with a higher quality one of the correct type which seemed to bring an improvement but likely was just coincidence, as the issue has persisted
• I've ruled out computer/equipment issues on the router side by bypassing routers, using different routers, using multiple computers to do tests.
• The issue is intermetient which makes it hard to replicate but consistently the connections will become extremely slow and speeds will fluctuate wildly with no change in local usage.

I've tried calling/going through the chat app/etc. but I can't get in touch with anyone to specifically address the issue, the one time I got through to a person, they suddenly transferred me to Netgear's (modem manufacturer) automated support line which just informed me that I don't have a warranty.

Tried calling back but again just got the automated "go to our website" which leads me to a loop of resetting the modem forever which of course, doesn't actually fix anything. 

At this point I'm not really sure what to do since there's apparently no way to actually have anyone look into the problem, and I've done everything I can from my own end.

On top of all this, like many others are reporting, I'm seeing extremely exaggerated numbers for what comcast reports my data usage each month as. Considering that I've always had the same work from home patterns, and I have traffic counters on my router (which legitimately all traffic has to pass through), and those same traffic counters report significantly less than Comcast does. Even if you added in the irrelevant internal LAN traffic that didn't go outbound, I wouldn't be able to hit Comcast's claimed usage numbers.

This stonewalling of automated support is legitimately the worst possible way of handling things. I can't even report a problem.