Yatta!
For future reference if anyone else happens across this issue: it was the Qualcomm Killer Network Manager app / service.
It’s not 100% clear to me what this app does, it appears to be some sort of network configurator which gets side-loaded with the NIC driver. I’ve since found this (fairly damning) review on PC Gamer which suggests that it’s attempting to team together different adapters to increase throughput. When I looked at the app on v8ninety’s PC it looked like it was continually cycling through different adapters rather than doing anything useful.
Potentially this could be a compatibility issue between W10 and the driver suite, and there’s every chance that there’s updated software available for it. However, we couldn’t immediately see any benefit to the app, and making changes to the network whilst connected remotely is akin to sawing through a tree branch you’re sitting on, so for simplicity we’ve just disabled it in Services.
From the PCG link there:
Don’t waste your time with the Killer Network Manager or DoubleShot. They cause more problems than they solve.