Had the same problem, had to adjust the switch under the cannon.

Just use a screwdriver to tighten the screws on the cannon switch. Mine did that too. Solve the problem and came back after a few hundred games. I guess it's the shaker motor and way to much bass from both fidelity kit and external sub. I suspect all these vibrations loose the screws a bit but hey bass is staying

What switch are you talking about exactly? Is it a switch under the playfield? I'm having the same issue with my ACDC premium. Just started acting up today, cannon auto fires itself 50% of the time, give or take.

Before you guys adjust the switch blindly, you should go into the switch test and verify the switch or run the canon test and see if/when its being triggered. It's not good advice to jump right to adjusting something.

The switches in question are underneath the cannon I believe. It's there to tell the cannon not to fire too soon.

I tightened the two screws for switch 61 (cannon home) as they were loose. The problem got a little better, but did not go away. I loosened them a hair, adjusted the angle of the cherry switch itself (as there is a little play) and it seems be working normal now. Switch 62 is the opto that the cannon mech blade swings through. Both 61 and 62 were working fine in the switch test prior to me adjusting #61. The cannon was firing as soon as it was lined up with the bell shot, which in switch test is exactly when the blade cuts the opto for #62.

If you don't fire the cannon, it will auto fire on it's way "home", right after the blade exits the opto? I'm just trying to figure out what could cause this behavior to begin with. Is it a problem with #61, #62, or a combo of both?

It's a manual switch adjustment. Keep "playing" with it and you'll get it right. Don't think its the opto based on what you are describing. Shaker and sub woofer can loosen up whole bunch of stuff!

My opinion also. Be patient try and test. You cannot do anything wrong if you are methodical with this.

Well, the issue came back again last night. It's auto-firing at least 50% of the time, if not more. There doesn't seem to be any rhyme or reason for it. Sometimes it will auto fire a few times, work fine for multiple shots, auto fire again, work fine, etc. Is it possible that the switch for the cannon (#61 Cannon Home) is flaky? Also, I saw that the screws for that switch were already slightly stripped, would a Ace Hardware or similar place sell screws that small, or would it be some sort of special order through Stern or other pinball parts shop?

Just solved this issue myself - the screws were actually coming loose that held the assembly in. Tightened them up and it was resolved again.

Are you talking about the two screws that go through the cherry switch? They are held by two small nuts (insert joke here) above the switch?

No the cannon assembly itself. The screws that hold it into the playfield backed out a bit.