Windows hello protection removing password login

Question

This issue have to do with that Windows magically can demand the bitlocker key.
I had a customer who had this issue on vacation and he couldn't manage this himself.
When he came home, he found the bitlocker key, but couldn't login, Windows Hello just said hello customer and verified the faceid, but never let him login. Pin-code was blocked too, I could change it on another computer, but not on his local computer.

When I got in support with Microsoft, there was a a method to solve this and it solved it.
You went into safe mode with cmd, opened the registry and and loaded the local machine hive from the right drive and added part called msoftware or something and then it was possible to enter the password for the account again. It's a passwordless attribute which you turn off.

What I seek is the method to do this, to use for other customers, for when the MS support isn't available, which it often isn't, as I work in evenings.

Thanks in advance!