Sometimes if you regrab/don't hold jump after landing on the boo before it splits, you'll die. I think the problem would happen if Mario bounced on the boo as soon as he turned away from it, i.e. it moved up slightly while interacting with it.
I have a nitpick concerning the star interaction routine: it only allows Mario to bounce over them and thus enabling the default interaction. I do not consider this a removal reason, though, so let's accept it. My advice is looking into this star routine in a possible next version.