Subject: What makes a pinball go in different directions launched at the same streng

I have an electronic pinball game that I play a lot.  I've 
observed that even though I always pull the launcher all the way 
back, the ball's image doesn't follow the same path each time -- 
sometimes rolling over the first, second, or third rollover -- 
without any predictibility.  The same holds true for coin-
operated pinballs.  Why?

Re: What makes a pinball go in different directions launched at the same streng