I have some questions that may help narrow it down.

1- In the backbox there are two adjustments that govern how the machine awards replays/extra balls. It also has a novelty setting. Hopefully you game is labeled. Check the "Game Adjustment" Switch. Given your score card, it should be set for "add a ball" Is it? There is also a "feature adjustment" that govern how many replays/extra balls actually awarded for certain thresholds on the score reel. There are three phone jack plugs. If one is plugged in, you will receive 1 replay/extra ball. Two plugs-two replays/extra ball, Three for three.

2- Each reel has wipers that orient the game on reel positions. Have you inspected these? I have run into a few of these that have lugs bent and touching each other...causing similar issues you describe.

almost forgot. Check the specials relay. you may have a contact out of adjustment. Once enerigized, it may be not be disengaging. This is where i would start. Do all of the reel values register properly prior to hitting the your 2 ball award? If so, I would think this relay would be the culprit.

The machine is designed when in "Add a Ball", when you achieve the three Laterns, the center reel will step once to change the combination of the reels. Is this what you are talking about?