Warwick bug

I was playing intermediate bots earlier, as Warwick, and noticed something potentially problematic. A couple times, I would have tower aggro, but when I ulted an enemy target (also under the same tower targeting me) I'd lose the tower aggro. Another time, I was outside of tower range, and ulted under a tower that had some minions but no allied champs in range, and again I didn't draw tower aggro. Has anybody else had this happen?