Ok, I finally managed to recreate it, and funnily enough, it "does" seem to like romances. Specifically variable increases seem to trigger it, but only in specific spots. Will have to consult the RPG Maker forums.
Edit: Ok, it's getting even funnier. Apparently the variable increase determines how much of the box shows. If the variable increase was 2 it would show half the box.
Edit 2: Aaand it is only happening with Azar's variable.