Good work! That required some independent thinking on your part.
I can't take the credit. My search for information about the Troublshooter you mentioned lead me to a site that talked about problems with Windows Update. Not my problem specifically, but problems in general.
It talked about the Toubleshooters and also had instructions for using SFC, which included running DISM as one of the steps.
Other things it mentioned that I didn't do were:
1. Stopping, resetting and restarting Windows Update
2. Clearing and resetting some cache whose exact name escapes me now