Partner Relationship status imposed despite breaking up

Following today's supposed fix of this mechanic, I tested the partner relationship setting by having two Sims become a romantic couple and then breaking them up.

Upon going into CAS and returning to the game, I immediately received a notification that the two Sims were partners once more.

What's worse is that prior to the update, I was at least able to fix this on my own using CAS.fulleditmode and toying around with relationship settings. Now I can't even fix it doing that.

The issue with the partner relationship status wasn't just marriages (though that was the most often cited problem relating to this bug). A relatively recent update (before today's) broke the partner setting in CAS in a way that it persists and imposes itself into a relationship between two Sims despite the player's attempts to dissolve that relationship.

[CM edit - adjusted title]