Comment 29 for bug 1669374

Here is some more info revealed during the blackscreen and taken from the vt6 after loggin in there:

Command "journalctl"

org.gnome.Shell.desktop[744]: (EE)
org.gnome.Shell.desktop[744]: Fatal server error
org.gnome.Shell.desktop[744]: (EE)
gnome-session-binary[726]: Unrecoverable failure in requested component org.gnome.Shell.desktop
gnome-session-binary[726]: Warning: app ’org.gnome.Shell.desktop’ exited with code 1
gnome-session[726]: gnome-session-binary: Warning: app ’org.gnome.Shell.desktop’ exited with code 1
gdm-launch-environment[704]: Pam_unix (gdm-launch-environment: session) session closed for user gdm