Experiencing similar issues with packet loss - former network engineer but know jack about docsis/"cable" technology. Your posts are disheartening as you've had this for three months and I've only been working with Cox support for about a week.
Just through googling I see tons of people having this issue, I don't know how it couldn't be an infrastructure issue. If you start experiencing packet loss the minute you leave your gateway it is either cabling or infrastructure, and I wish their phone techs were able actually look at issues and not just "Oh we pinged your modem and it's fine."
If it's an intermittent problem you have to look at logs and see what's going on, you can't just say "looks fine now". I find it insane that their extent of troubleshooting is 'pinging' the modem. I asked if they have looking glass tools or anyway of looking at logs, which of course they don't.
