It would seem that from 1903 onwards, thunderbolt 3 networking has been broken in Windows 10, still broken in Build 2004. We have a QNAP TVS-872XT NAS, we see about 1000mbps write and 1400mbps read on our 13" Mac Book Pro. We have two Windows 10 PC's with thunderbolt, one Ryzen, one Intel, both tested with an external thunderbolt drive with 2m active cables get's 1.4gbps read and 1000+ write speeds.
It's not the cables, both are tested and pass because of the external thunderbolt drives and speeds.
It's not the NAS because it works perfectly with the Mac Book Pro.
It's not the Thunderbolt cards on Windows because they work with the external thunderbolt drive.
It seems to be Thunderbolt Ethernet, it's fundamentally broken, 65mbps transfer speeds copying from, and trying to copy to it drops to 0mbps and then nothing.
Many folks have exactly the same issue here
QNAP appear to have reached out here:
I'm at a loss, I don't think there is much more I can test or try, both windows machines have exactly the same problem, clearly, thunderbolt 3 networking on windows is now broken, is there a hotfix available.