From the schematic, you can see that as long as the AX Reset Relay is tripped, the bonus unit will fire 5 times per cycle regardless if it is at the "0" position or not. This is kind of a flaw with Fast Draw & Quick Draw - they should have put a "0" position switch in the reset circuit because 99 times out of a 100, the bonus unit is at "0" at the beginning of a game (because it counted down to "0" from the previous game). So the bonus unit pounds away needlessly about 50 times at every game start. I say it is a flaw, but they probably did it on purpose to save a few bucks on a switch and a few feet of wire. So, anyway the bonus unit is not your problem (it is acting normally) - you need to figure out why the score reels aren't resetting.

The unnecessary beat down on the bonus unit (usually the coil stop needs replacement and/or the plunger is shroomed because of this) can be "fixed" by putting a piece of tape across the AX switch contact with the Blue-Orange wire (or bending the blade slightly so it doesn't close when the AX relay is tripped). That's the easy way, and the only time it would ever make a difference is if you ever shut off the game when the Bonus Unit wasn't at zero (which is almost never), and even then, it would resolve itself after you play the first ball on a new game.

Or you could really do it right, and put a new "Open at Zero" switch on the Bonus Unit and wire it to the AX switch.

Sure it does. All EMs do that, but you don't score any points of course. The subtract bonus circuit we are talking about in this thread is only active when the game resets (AX relay is tripped), so it does not take away any functionality of the game if you disable it.

My apologies - upon closer review of the schematic, you are absolutely correct that the bonus unit will reset itself from a non-zero state via relay E when the machine is turned on. So, now I really don't what the purpose of the AX switch in that circuit is, except to make noise during game resets. It is a good question!

Even if you tilt on the last ball, the bonus unit will reset itself before the machine goes to Game Over.