Gottliebs are infamous for the ball hitting the underside of the apron. The ball does not sit on the kicker arm because the outhole gets elongated. There's a fix that involves using an old switch blade to hold the ball in place better.

Could also be the mech itself or the switches mentioned above.

Look in there and see if it is hitting the under side of the apron .

Not one of Gottlieb's better designs. Williams and Bally outhole kicker systems are far superior

I've owned four different Bally games, and none of them ever had an issue, other than just the normal dirt that basically all games have under the apron. Even when dirty, they kicked reliably and strong.

The Gottlieb design just has too many moving parts to it. Gottlieb did a lot of things right, and better, but score reels and outhole kickers were two that were not better.