Cannot change admin PW

[crtrrss]

A client dropped off a Macbook Air that needed a keyboard replacement. Her child sprayed Lysol all over it and fried it. She originally took it to the apple store. They took it apart and forgot to plug the battery back in, and then quoted her for like $400 to fix it, plus shipping. Ridiculous. I plugged the battery back in and I'm replacing the keyboard when the new one arrives, but the password she used no longer works, even with an external keyboard. I reset it both online with her apple ID (had to manually enter date and time for it to connect too, if that changes anything) and offline with the HD password, but my changes seem to be reversed every time I reboot. The same old hint is there in the PW box, despite me changing it too. Does anybody know of a workaround for this?

TL;DR
I changed a PW in MacOS Recovery Mode and every time I reboot to the main OS, it reverts to the original password and won't let me in. How fix?


What I've tried:
-"passwordreset" in terminal
-normal reset through reset tool after boot
-resetting using Apple ID
-resetting using HD password

All to no avail

 

[BLUEDOG314]

Is filevault on? Also did you attempt to separate Apple ID password from computer password? I have only ever ran into trouble when linking computer password with Apple ID, and allowing reset from icloud. Try turning this "feature" off and see if that helps.