Superminions Should have structure priority

I've played so many games where the super minion was on the nexus towers and they were one hit away from being destroyed but all of a sudden they target oncoming minions. It's so frustrating to see them stomping around the tower and hitting minions instead of what's infront of them. My suggestion is that they should not change targets once they have locked on to the tower/inhib/nexus. It makes no sense why they change targets, maybe it's a bug and something's wrong with their targeting who knows.