I too was having the issue with ethernet on Ubuntu 16.04 at 4.8.0-51.
I also have the DA200 adapter:-
http://www.dell.com/en-us/shop/dell-adapter-usb-c-to-hdmi-vga-ethernet-usb-3-0-da200/apd/470-abqn/pc-accessories
If I plug this into the ethernet port on the TB16 and use the ethernet port on the DA200 my ethernet hasn't dropped out in the last hour. I've tested with copying large files from my NAS, from the net and NAS and net concurrently.
Let me know if I can provide further details.
I too was having the issue with ethernet on Ubuntu 16.04 at 4.8.0-51.
I also have the DA200 adapter:-
http:// www.dell. com/en- us/shop/ dell-adapter- usb-c-to- hdmi-vga- ethernet- usb-3-0- da200/apd/ 470-abqn/ pc-accessories
If I plug this into the ethernet port on the TB16 and use the ethernet port on the DA200 my ethernet hasn't dropped out in the last hour. I've tested with copying large files from my NAS, from the net and NAS and net concurrently.
Let me know if I can provide further details.