[Edited]
My theory DOES hold water. I tried creating a phantom spouse name with RIN=0 in the NameTable using SQLite. However, it took closing and reopening the database in RM8 to see the effect I surmised I would see.
I added only one record to the NameTable with the name “*Phantom, Fake” and set its OwnerID to 0. The name does not come out in all screens because the program substitutes “Unknown spouse” in some. Were it to do so consistently, you would be unaware of the phantom name but its existence might be a trigger for some other unwanted behaviour.
I would still submit your database to Support along with your explanation of what you observed and a link to this post. You may not be able to recreate the issue but it would be helpful to others if Support has already analyzed it and can correct the data, even if they, too, cannot replicate the actions that caused it in the first place.