A number of friends and I have tried several DISM variations using non-Windows-Update (non-default) sources. Here are known successes. /LimitAccess means don’t use Windows Update.

The first one presumes that a different machine running the same OS is available on the network with C$ being the C: drive share. Reportedly, that share can be simply all of the files from a non-running install.

DISM /online /cleanup-image /restorehealth /source:\\ANOTHER_SERVER\C$\Windows /LimitAccess

The second one uses an OS install ISO; right-click it and choose Mount. G: represents the drive letter given:

DISM /Online /Cleanup-Image /RestoreHealth /Source:wim:G:\Sources\Install.wim:2 /limitaccess

Many ISOs have more than one image within the .WIM file. To get the list of images (and numbers to put after the colon), run this:

DISM /Get-WIMinfo /wimfile:G:\sources\install.wim

You’ll notice, in the /Source:wim line above, that #2 is present, not #1. This is because, in a very common image recently used, it is image #2 which has most of the components, not #1.

After a DISM /RestoreHealth is successful, it appears to be best to run SFC /SCANNOW. To some extent, DISM appears to get the good stuff in, and SFC appears to put it where it needs to go.