NIB and auto-firing, that's cool!

The opto is located around the 'half moon' part, that rotates with the cannon.
There are 2 switches for the cannon as far as I know, both should be checked and might be adjusted in your case.

Make sure the screws are tight that hold the opto, that fixed mine.

Mine does this, but only on occasion. It's like the ball gets loaded, Steve says "Get ready...", and then the canon cranking noise goes silent, the canon swings out and back and auto fires. It's got to be opto or switch related, but I haven't looked into it yet.

the same problem at my NIB Premium

it must be a problem with the optoboard

but in switch test both switches are working fine!

Is this common on the latest run? I'm replacing my pro with a premium tomorrow and I hope this is not a common issue.

Mine's a first run LE, so it's been around for a while. Not every game does this. I'll check the optos out this weekend.

i had to push the cannon manually back to the home postion to line up with the 'home' opto.. just a minor shift.. has worked great since.

After a couple months of ownership mine started doing this. I did a switch test and they are all working. I poked a screwdriver over the Switch#62 opto and can manually trip it.

Watching the cannon from underneath, it autofires immediately upon triggering switch 62.

Not sure what else to look at. hmmm..

There is a game specific test for the cannon in diags. With the test started and the coin door closed, push the start button and the cannon should rotate about 1/3 of the way out and stop. Push the start button again and it should rotate all the way out and back to the home position without stopping. While running the test, watch the DMD to see that the switches are working properly. If the two micro switches are working properly, you have an opto issue.