Post Windows 10 Update Login Problem

In the aftermath of updating Windows 10 a customer was presented with a different looking login screen and had their PIN number rejected. I guessed correctly that the customer's Microsoft account (cloud based) had been set as the new login method. The fix was to use another computer to perform a password recovery at login.live.com.

I'm seeing all manner of odd changes and problems after the large Windows 10 updates that have been coming down in 2018 including login issues, programs not working afterwards, computers stuck in loops where the update won't complete, privacy settings changing to reinstate disabled Microsoft Store apps, etc.