I know this is an old thread, but I recently purchased a T2 and have some details to share. It was shopped when I bought it, so everything was right and tight. The kickback would send the ball into the top 3 diamond lanes every time. I took this to be a little 'bonus' of the kickback, and expected it every time it fired. Slowly, after 75-100 games, the ball wasn't travelling as far up the 'chase loop'. The coil and kickback lane itself were fine, so I inspected the 'chase loop' lane the ball is sent into. The ball kind of slams into the outer wall of the 'chase loop' when it comes in, and ricochets off the inner rail with enough energy to make it up to the diamond lanes. But I noticed the inner rail looked like it had been replaced and was askew and slightly loose - resulting in a loss of energy to the ball when it bounced up the lane.
I removed the rail, wrapped some fine tape around each end to 'thicken' the post, and tapped it back in. I also tightened the screws on the outer wall. Voila - it travels back up to the diamond lanes. IMO, this is how the kickback should function.
Hope this helps.
Terminator 2: Judgment Day