Quoted from TomDK:I only figured out that it hapens sometimes in multiplayer while counting the bonus , a extra ball is given on ball 3 but the game went on to the next player. So the animation ws there but no chance to get this extraball.
Are you sure it's the extra ball being awarded or it's telling you extra ball is lit?
At the end of your third mode it lights the extra ball, so if you're in a your third mode when you drain your last ball it lights extra ball as the mode ends. Seems like it would be better if you were on your last ball and drained it wouldn't show that though..