(Bob, Yes, I did see your note about the conversation with the Microsoft Insider.)
Hi William,
Well, very interesting, and surprising! I did the sfc /scannow experiment:
CMD.jpg
So changing the version or date properties clearly changed the hash, which sfc picked up. In the CBS.log file (attached if you're interested) you can search on "do not match" and see two sets of eight non-matches, at 12:38:46 and 12:38:51, for just the two files msjet40.dll and msrd3x40.dll. No other mismatches were detected anywhere else.
For the final test of the successful non-repair, the only time you might root for a repair to fail, I reloaded the schedule browser several times, as Bob had indicated earlier, and saw no growth in the size of either .dll file. So "sfc" did indeed leave the good (old) .dlls in place.
I don't know if this means anything for some kind of permanent solution, but it's an interesting result. Thanks for sharing your know-how.