Hello, I am doing a project for my class where you simply just make a single player pong game yet whenever I issue the command if on edge bounce my ball just teleports randomly when it hits the edge of the screen. This happened everytime I used it even with just move command and bounce, nothing else. I tried looking up videos on youtube, copied them exactly the same and yet it still does the same thing. Help?

http://scratch.mit.edu/projects/28578734/

The third (smallest) ball's costume centre is off. Use the costume centre tool (the button that looks like a plus sign) and click on the centre of the ball costume.