Hi TreeMan,
checking your CBS log, it states:
Repairing corrupted file \??\C:\Windows\Web\Screen\img100.jpg from store
Repairing corrupted file \??\C:\Windows\Web\Screen\img105.jpg from store
Repairing corrupted file \??\C:\Windows\Resources\Themes\aero.theme from store
Do you replace the theme or delete that folder, or maybe removed Lock Screens component earlier?
If the latter, it will be fixed in next.
Thanks.