Quoted from RacerRik:

I have a question about this also. My IJ used to pop the knocker for every extra ball. I was changing batteries and unfortunately lost the memory. After setting it all back up, it only knocks once in a while - not at every extra ball. I don't know what setting would cause this. I have it set for free play, fixed replay scores and extra ball awarded for replay scores.
What setting is needed to get my extra ball knocks back?

Quoted from RacerRik:

I do have the replay award set to extra ball. It knocks when I score an extra ball via the 8X lane award and when I get the extra ball from the path of adventure. It does not knock when I score an extra ball from the replay scores.

Quoted from RacerRik:

Special is set to extra ball. Match is set to off. I left ticket dispenser settings at factory default. Thanks for helping me with this!

Quoted from RacerRik:

I think I figured it out. It seems that turning on Award Ticket for extra ball causes the knocker to fire on every extra ball. Not entirely sure because I was changing too many things at one time - but I got my game working the way it used to work.
Every extra ball now gives a satisfying CRACK!