Quote:It appears that the list of bugs in Windows 10 version 1809, the October 2018 Update, is still growing despite Microsoft's efforts to fix these bugs.

Microsoft's Japanese Ask the Network & AD Support Team confirmed another bug in Windows 10 version 1809; the bug may occur when devices running Windows 10 version 1803, the April 2018 Update, are upgraded to Windows 10 version 1809.

According to the report, the built-in Windows 10 administrators account may be invalidated during the upgrade. In other words: it cannot be used anymore because it is broken after the upgrade.

The bug occurs when the following two conditions are met:

• The built-in Administrator account is enabled (it is disabled by default).
  
  
• There is at least one additional account with Administrator permissions.
  

Microsoft reveals that it is working on a solution for the issue; the company asks administrators not to upgrade to Windows 10 version 1809 on devices on which the built-in Administrator account is the only account with elevated privileges as it would block access to administrative functions on those devices.

Administrators are asked to make sure that at least one additional administrator account is accessible on devices before the upgrade to the new version of Windows 10 is started.

Full reading: https://www.ghacks.net/2019/01/02/windows-10-version-1809-upgrade-could-invalidate-administrator-account/