Steps to reproduce:
1. login in a tty to verify your password work fine.
2. Open "User and Groups" app, got to Advanced Settings and add some privilege to your user.
3. login to a new tty and see that your password doesn't work. Try with empty password and see that it works.
4. run `passwd $USER` to set user password again and repeat 1 to 3, in order to verify the issue.
I haven't tried, yet, any other tasks from User and Groups application to see what impact they have.