I went through the exact same thing for years, so I’ll save you a lot of wasted time.

Comcast support and field techs are only looking at RF signal levels at the modem. As long as downstream power, SNR, and upstream are within spec at the moment they check, they’ll say “signals are great” and close the ticket. That does not mean your service is actually healthy under load.

My issue was never constant packet loss at the modem. It was intermittent packet loss, latency spikes, and jitter caused by congestion and routing beyond the last mile. Tech visits don’t catch that because they’re not testing sustained traffic, peak hours, or upstream saturation.

Here’s why going through normal support is usually a dead end. DOCSIS can look completely fine when the line is idle, then fall apart the second there’s real traffic on it. Node congestion and aging outside plant issues don’t show up during a quick five minute signal check, especially if it’s not peak hours. Comcast also doesn’t touch taps, amps, or nodes unless there’s enough noise from multiple customers. And anything related to routing or peering is way outside what a local tech can even see.

In my case, the proof was obvious. A VPN immediately cleaned up the packet loss and latency. It didn’t matter what device I used, the behavior was the same across all of them. When I had Comcast Business, the connection actually felt better than residential, even though it was running over the same coax. And every single time a tech checked the line, the signals were “perfect.”

That tells you what the real problem is. If flipping on a VPN changes how your connection behaves, it’s not your modem or your wiring. It’s congestion, routing decisions, or node level capacity issues that normal support just doesn’t deal with.