When I change to a virtual terminal (e.g. tty3) by hitting Ctrl+Alt+F3 I can not log in.
After entering my username and hitting Enter the terminal somehow starts "virtually hitting enter". It just does not let me enter my password but immediately complains "Login incorrect" asks again for the username and continues as if enter is pressed with an empty username. This continues for 5 times until the terminal is "reset". Then enter does not seem to be pressed anymore. When I enter my username again and hit Enter the procedure starts again.
My first idea was that my enter key hangs. But in no other circumstances this happens, neither in the X environment nor earlier in grub. I tried it with an external keyboard plugged to my laptop and without. It is always there.
I'm using Ubuntu 18.04.1 with a quite fresh install. Nevertheless I have my user account recovered from an older installation, but not the system configuration. I have no idea whether this problem existed from the beginning or when it started. I just realized it now.
Does anyone has an idea where the problem could come from?