Getting locked out of an active session

Sometimes happens that I lock the session and when I want to log back in, I can't actually click inside the password field to fill it in.
It happend when the display goes off while locked and not always. Given that I got locked out I don't know what else I can do to troubleshoot and provide more info.
BTW, I was able to use Alt+F1-6 to use other terminal and log in, just don't know what to check ATM. Also I was usually in a rush so I simply restarted and possibly lost some unsaved data.