I've made a simple animation of a cannon shooting a ball chosen by the user. Basically, I want my user to be able to drag the ball to the cannon, drag the lid over the ball, and have an animation play. I've got it so that it works most of the time, but on (what seems to be random) occasions the animation won't play. What's really strange is that if you select the blue ball the animation wont trigger on the first open of the site, but does just fine after you refresh the page. 

I've got more hours than I can count into this so if you have any ideas I would really really appreciate it!