Resetting a password gives me an internal error occurred message
I forgot the password to my Mac.
When I leave it for about a minute it asks me to press the power off button and then power on and go to the recovery OS where it goes through a process to allow you to reset your password if you know your icloud account info.
I go through the process successfully until it asks to type in the new password and confirm it and then add a hint. I do this successfully and then I when I click on 'Finish' I get an 'internal error occured' and it asks me to restart again.
Nothing that I can do get's me out of this cycle.
Can anyone point me to a way this can be solved? What is this internal error that is being mentioned?
MacBook Pro with Retina display, macOS High Sierra (10.13.2)