Hi Eric,

Sorry about the delay in getting back to you!

These are some really good troubleshooting steps that you've done. So it sounds like you've ruled out the TCP stack on your gaming PC, your NIC (the IPv4 IP), and your modem as the other PC is connected directly and has not had issues.

So it sounds like it's either the cable between gaming PC and your router, the cable between your router and your modem or else the router itself somehow. Have you done a factory reset on the router? To do this just google the router make and model and "factory reset". It's possible if you're router is a bit older than it could be starting to fail. Often a factory reset kicks things into gear.

If that still doesn't work I'd suggest getting a known good cable (between the other PC and the modem perhaps?) and try that with the gaming PC. You could also try different ports on the router as well.

As far as packet loss on intermediate hops, you're correct, no need to worry about those if the final hop is clear.

Let us know how it goes!

Thanks,

-Poe