OP

Quoted from apple550:

So it seems I was just driving myself crazy. At some point I observed this phenomenon during games which is what prompted me to investigate. Unfortunately from that point forward I was only testing using the clear ball function. It seems the clear ball function itself can cause the game to eject multiple balls. This makes sense, as I noticed that often the amount of time between when I pressed the button and when it would fire was highly inconsistent. No such inconsistency in coil test mode.
So naturally I invited my whole family over to play the game for hours, and believe it or not the problem never arose. Yet going back to the clear function it will happen again, and again, and again. So a warning to anyone attempt to test this way, the test itself can at times be the problem itself.