tty do no work after putting laptop on docking station

On ubuntu 18.04 using gdm3 and gnome-shell, getting into virtual consoles works well when the laptop is not on the docking station. After putting it on the docking station (getting then 2 monitors), using CTRL+ALT+F{3,4,5,6} freezes the GUI. I can come back to GUI using CTRL+ALT+F7.

However, after going in text mode ("systemctl isolate multi-user.target") and restarting gdm3, it works again, even if already on the docking station.

It looks like putting the laptop on the docking station make this bug happen. It does not happen when the laptop is booted on the docking station.

Description: Ubuntu 18.04.2 LTS
Release: 18.04

gdm3:
  Installé : 3.28.3-0ubuntu18.04.4
  Candidat : 3.28.3-0ubuntu18.04.4
 Table de version :
 *** 3.28.3-0ubuntu18.04.4 700
        700 http://fr.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        700 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
        100 /var/lib/dpkg/status
     3.28.0-0ubuntu1 700
        700 http://fr.archive.ubuntu.com/ubuntu bionic/main amd64 Packages

gnome-shell:
  Installé : 3.28.4-0ubuntu18.04.1
  Candidat : 3.28.4-0ubuntu18.04.1
 Table de version :
 *** 3.28.4-0ubuntu18.04.1 700
        700 http://fr.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     3.28.3+git20190124-0ubuntu18.04.2 700
        700 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
     3.28.1-0ubuntu2 700
        700 http://fr.archive.ubuntu.com/ubuntu bionic/main amd64 Packages