There is a cosmetic issue with e1000e driver versions lower than 2.2.14.
To confirm that this is the cause of the problem:
Do one of these to set the state of the interface to "off":
In Gaia Clish, enter these commands to check the link: [Expert@HostName:0]# ethtool <NAME>
The output shows:
Link detected: yes
The interface's LED on the Gaia machine stays on (no data, not blinking).
On the switch, the corresponding port is still "up" (operational status).