Dell Precision 5520 using TB16 Thunderbolt dock having lan issues

We have a Dell Precision 5520 that uses a TB16 docking station that all of a sudden is having difficulties connecting to our VPN. It was fine earlier in the day. We tried clearing the DNS cache and tried a winsock reset. THe drivers are up to date and everything. 

Also tried to reboot the computer multiple times.

Even tried a K17A Dock and had the same issue.

We were finally able to get the computer to connect to the vpn once we used a usb net adapter to plug the ethernet cable into.

Tried plugging the usb adapter into the computer directly and into the dock. It worked whether it was directly connected to the computer or the dock.

It only does not work when we connect the ethernet cable to into the lan port on the TB16 and K17A dock. And only for the one computer.

At a loss, any ideas?