During our imaging process we change the lock screen picture to show that imaging is in progress and we change it again when the process either completes or when it fails.  There has been an issue with a very small number of machines when the task sequence fails in that the lock screen gets stuck on the failure lock screen even after the problem with the upgrade has been fixed.  The solution is as follows.

Open an administrative command prompt and run psexec -i -s cmd.exe . If you don’t want to use psexec or you don’t have it, you will have to take control of this folder as you won’t have access to the folder as an administrator.

After that navigate to C:\ProgramData\Microsoft\Windows

There you will find SystemData folder.

Now either rename the folder to SystemData_bak or delete it (your choice).

To delete the entire folder use RMDIR “FOLDERNAME” /S /Q 

Finally restart explorer. Open Task Manager, find Windows Explorer and click on Restart.

Now log off and you should see your correct lock screen.