[GAMEPLAY] Quinn's vulnerability targeting structures

Was practicing adc with Quinn in a custom game by myself. After I was pretty much finished I decided rather than just leave I would push through to the nexus and finish.

I noticed that when I hit a vulnerable minion and then immediately switched to the structure I was currently fighting, Quinn would continue to hit the structure as if it was marked as vulnerable (as in, dealing extra damage and visually firing multiple crossbow bolts on every single shot after hitting the marked minion). It happened twice, once on the inhib and then again on the nexus.

Once I stopped hitting that structure, everything went back to normal; but as far as I know, this isn't supposed to happen.