Had the same problem.....I added two blue rubber 1" x 1" x .25 to the end of the rail as shown. Problem has been solved ever since. However, I removed the Cliffy color post because my shooter rod on the steps lane strikes the ball just off center causing a nasty bounce off the Cliffy post. Cant seem to get the shooter rod on center.
P.S. Yes, the side rail wood is red.