On the FACTs screen, what is Preferred on the Shared Marriage FACT is the 1869 DATE of the Marriage. Remembering that even if there is ONE Marriage FACT for JS, the single Shared Marriage FACT will be Preferred. If there are multiple Shared Marriage FACTS, one of them will be preferred.
So, that page has nothing to do with this issue.
Yes, the Relationship button is was not expected.
What does AJM's first wife say?
If you go to JS's Relationship Button,
How many Parents are listed?
If there is more than 1 Mother and 1 Father, which is marked at Preferrred?
Do you see any "unknown" relationships on either JS or AJM Relationship Buttons?
If you were to Export your File to a GEDCOM file, how large would that GEDCOM file be (in Kb)?