The dreaded "can't find source" error. Good Luck. Downloading the windows.iso and using the sources switch did not work for me. Using Media Creation Tool to "upgrade" did work.
*It's wise to have stuff backed up.
First I tried this . . .
Download win install ISO
To read index of versions in Windows.iso
Mount the ISO then cmd as admin:
dism /Get-WimInfo /WimFile:[drive_letter]:\sources\install.esd
To read more info about each version:
dism /Get-WimInfo /WimFile:[drive_letter]:\sources\install.esd /index:1 (or whatever)
If you want to export the wim version to match (change "IndexNumber")
dism /export-image /SourceImageFile:install.esd /SourceIndex:IndexNumber /DestinationImageFile:install.wim /Compress:max /CheckIntegrity
*This saves some room but not worth the trouble
DISM /Online /Cleanup-Image /StartComponentCleanup
DISM /Online /Cleanup-Image /AnalyzeComponentStore
DISM /Online /Cleanup-Image /RestoreHealth /Source:WIM:c:\install.wim:1 /LimitAccess
or
DISM /Online /Cleanup-Image /RestoreHealth /Source:e:\sources\install.esd /LimitAccess
Yes, I tried without /LimitAccess.
This is what I kept getting . . . And sfc /scannow would find errors it could not fix
(On one PC I get this error and can't get any fix to work.
Error: 0x800f081f
The source files could not be found.
Use the "Source" option to specify the location of the files that are required to restore the feature. For more information on specifying a source location, see https://go.microsoft.com/fwlink/?LinkId=243077.)
So I did an "upgrade" with the Media Creation Tool which didn't really upgrade anything but did seem to reinstall the system and kept my installed programs with few alterations to the basic system. This is not a "reset" which will remove your installed programs. It seems Windows always has a way to install repair over the current version. Yes, sfc /scannow now gave a clean report.
(C:\WINDOWS\system32>DISM /Online /Cleanup-Image /RestoreHealth
Deployment Image Servicing and Management tool
Version: 10.0.19041.844
Image Version: 10.0.19045.2846
[==========================100.0%==========================] The restore operation completed successfully.
The operation completed successfully.)