I had the same exact problem with my TMNT that I bought last September. The auto-launcher would work 3/4 times correctly and that one time it didn't work would ruin the whole multiball. I tried changing the coil and spring, but that didn't help. The problem ended up being that the shooter rod was too long so the arm for the auto-launcher didn't have enough movement to get the ball up the shooter lane. This is the shooter rod I bought and am currently using in my TMNT: http://www.marcospecialties.com/pinball-parts/26310