If the 0.47 caps are the originals they can cause false triggering of switches to occur so many people just cut them off. You can try remove the caps from the pop bumpers to see if this will stop the double firing. The random firing could also be a set of switches being too close together and touching due to vibration. You will need to look at every switch and check there is enough gap between the blades. The switch test built into the game is useful for showing which switch is stuck on.
regards Derek
