I just got my first machine over the weekend, a very nice 2007 Spider-man that looks and works 100% except one small catch. Occasionally, the ball won't spit out into the shooter lane on ball start. You can hear the trough fire, but no ball. If I open up the coin door and manually eject the ball (this takes a pretty forceful hit), the machine will spit out another ball immediately afterwards putting 2 balls in the shooter lane. If I turn the machine off and on again, it will spit out all four balls into the shooter lane for each "ball" for the whole next round. After that, it resumes play as normal for about 10-20 plays or so. What could be the problem here?

For full disclosure, I'm a complete newbie.