I've had a continuing problem with my World Cup Soccer. It occasionally and randomly ejects balls into the shooter lane during a game. It's very unpredictable. For example, I played 10 games tonight with no issues and then it started firing additional balls into the shooter lane and stacked up two or three. I've noticed it happens more often when the slingshots are both kicking back and forth or during multiball. I also noticed today that it might be related to the right flipper. The opto transmitter board has been replaced and the optos have tested out okay. No issues with any switches firing on the switch test when I bang on the playfield. Any ideas on what could be causing this? Ideas for what to try? I've considered replacing the 7 opto switch board - am I on the right track?