Was working on a friend's Mac and required a password she couldn't remember. Used single user mode as a start up option and changed the password and rebooted but then was unable to login. It lets you login for a split second without showing anything then kicks you back to the login page.
I then created a new admin user using the single user mode which worked OK but the new account has the same issue.
Booted in to recovery mode and was unable to mount the internal drive and it had issues. FSCK isn't able to fix them after multiple runs.
Have I really just got unlucky with a drive while in use?