This is looking more and more like a widespread issue. Up until about 10 days ago, my service was so great that I actually made a post praising Cox for their great quality.
Now, like many others on this forum in the same area, I'm getting T3 timeouts, DRW violations, and severe packet loss of up to 35% on the upstream. The common factor in almost all of the posts you linked seems to be problems on the upstream. Some also have downstream issues, but upstream appears to be more common. Like you I've dug into the DOCSIS specification and documentation, and I came to the same conclusions that you did about possible causes.
Here are the possibilities that I see:
Everyone's modem and/or interior cabling went bad simultaneously around August 1st. I hope no Cox support techs think this is a real possibility, even though they always try to blame the modem.
There are multiple individual network issues that all started around August 1st. A slim possibility at best.
There is a widespread issue but Cox is not aware of it yet. In this case, these reports need to be escalated to someone who is empowered to review them as a group and investigate the overall pattern.
There is a widespread issue, Cox is aware of it, but support has been directed not to disclose the issue. I hope that's not the case, but it would at least mean there's hope of getting it fixed someday.
Some of us are likely going to need to schedule tech visits to get this escalated to the proper levels. That's too bad because it wastes our time and Cox's time, but there might be no other way to get it resolved. If you're confident that your modem and cabling is good, it's worth it to have a tech come out. They threaten a $100 charge but I've never seen anyone get charged the fee unless it was a really obvious problem like having an unplugged coaxial cable or forgetting to connect power to the modem.
I’m from the Las Vegas area and my areas service went down for a week, came back even faster then before. Now it goes in and out at random times. Sometimes it’ll be 3 pm and other times it is 3 am. I notice my modem started to restart itself around the same time. Also, it used to say there was an outage in my area for about a month and not it says nothing when I log onto cox.
This wasn’t in August though. It was 2 months or more, whenever the initial outage occurred. It seems to occur more and more though and online school for most of the state is about to start.
I understand how frustrating an off and on issue can be to face and wanting to get to the bottom of a solution. We may need to reserve a service appointment to help identify what's causing the service disruption outside of the outage alerts from before. You may email support at Cox.Help@cox.com with your complete address and details of the issues happening now.