What I am doing is simple.
I boot.
I get the graphical environment/display offering the user list (X).
Now 2 options
1) I login "normally" bu providing a password.
After that, the graphic freezes for a small while (1-2 Minute),
and I can try the same thing, wit the same result.
Does the login user have a VNC server running? If I connect
a monitor to a normally headless server something similar
happens. VNC servers are being started using systemd.
Only one solution: reboot (for example by login from the network).
2) Ctl/Atl F2. I get a text terminal and I log in text mode
I run startx and the X mode opens, every thing run properly
(gnome).
Do you
Is it clear?
I haven't tried that -- just use the text terminal to stop the VNC
server.