Edit:  I was using the latest drivers from TP-Link support dated 08/03/2020.  I since found more recent drivers on Marvell's website and updated to v 3.1.6.0 dated 12/17/2021.  Behavior is still the same, although when not affected by whatever this is after waking up from sleep, this version does seem to be maybe a little faster.

  @Solla-topee Thanks for your reply.  The issue is 100% reproducible every time the PC wakes from sleep. Here are pictures of my normal results and the result about a minute later after waking from sleep mode:

Adapter stays linked at 5Gbps (I keep it on auto-negotiate, but I have tried forcing it to 5Gbps manually.  The issue remains either way.

Driver version as mentioned earlier:

System info.  If this isn't the page you want I could export to a file and send it, maybe.  Let me know if this is ok:

  @Solla-topee Sorry, you asked for topology and I forgot to include that.  I have the AT&T BGW320-505 model.  There are 4 ethernet ports on this router, three are 1Gbps and the 4th is a 5Gbps port.  The PC in question here is directly connected to the 5Gbps port of the router with a brand new Cat 6A cable.  I first tried with the cable included with the TX401 adapter.  The first thing I did when I noticed this issue was change to a different brand, new Cat 6A cable.  The behavior persisted, so I tried a 3rd Cat 6A cable from yet another manufacturer, and it made no difference either.  I don't think the cable is the issue.

Thanks again for your interest and please let me know if you have any further questions or if I missed responding to anything else that you already asked.