I updated the ethernet driver, and checked for bloatware - nothing there. I also looked at the links you provided and they are either not pertinent to this situation or I've done them already.
In looking at the Ethernet utilization on TM I noticed an interesting pattern as shown below. The downward spike of send and the upward spike of receive overlap. Also you can see the spike downward in GPU simultaneously and that the upward spike in receive happens just prior to that. Hard to know what is cause and effect, and I can't determine the exact sequence and timing of the various pieces we're observed; cpu threads spikes up, GPU down, Ethernet both. If we could get exact timing we might find out more about the cause and effect piece.
So we have a lot of observation