Yes, it is another Windows 10 bug and the update should be renamed to 'FAIL Creators Update'
After investigating the problem, I discovered that Windows 10, during the update, has created – for unknown reasons – a new temporary profile and then loads this profile as the default profile for the user. The following issue is occurred on a customer's computer, after installing the Windows 10 Fall Creators Update (v1709): Windows displays the error 'We can't sign into your account' after sign-in and all the user's personal files and the installed Store Apps are missing.
