When you start the game, do you hear the chime strike and then lock on? If so, disconnect the playing field and then the problem is there (on the playing field somewhere). I can't believe the sling shot is the only 10 point on there and I've owned 3 Pro-footballs.

Or does the "N" relay stay locked on after you hit the sling shot. If so, I would say look at the gaps on the "N relay" or even the score reel. Could be too tight.

Should be an easy fix since the problem just occurred. And don't loose sleep over it...best thing is walk away and come back later. Most my answers come to me while my eyes are shut!

Good to hear!
Go have fun playing football!