I too have this problem with a Dell Precision 7520 attached to a TB16. After reading this bug report, I wrote a simple script, tb16_speed_limit, which I have attached. Place this in /etc/NetworkManager/dispatcher.d/pre-up.d in order to limit the connection speed to 100Mbps.
I too have this problem with a Dell Precision 7520 attached to a TB16. After reading this bug report, I wrote a simple script, tb16_speed_limit, which I have attached. Place this in /etc/NetworkMan ager/dispatcher .d/pre- up.d in order to limit the connection speed to 100Mbps.
This might help @zwigno