Just this AM, the Windows Repair "Permissions" (repair 1, 2, and 3) was run to repair my wifes problem saving Word files and after the repair, all her quicken files became visible opening the application, so that problem was fixed (probably temporarily) with something done during job 1, job 2 , and/or job 3. I shall try the "repair install". I do have a copy of build 17134 on a bootable USB stick, and a copy of the latest cumulative update to that, 17134.165 on another USB stick (having 8 Windows 10 computers almost necessitates downloading these once and saving them rather than downloading them 8 times).
Thanks for the suggestion, I should have thought it myself, but somehow overlooked that solution. I'll give myself 30 lashes with a wet noodle for punishment.