Hi Sam.
I'm sorry I didn't press the Comcast tech more. I'm not sure the tech even knew what they were doing other than going through some standard fix procedure. I think they "activated" or "reactivated" the GTV, whatever that means. Then they remotely restarted the gateway and things seem to be working much better now. I still get the occasional stutter and freeze but much less.
Does any of that make sense?