I'm sure everyone else will chime in but if you have not replaced the harness, that would be the place to start. It's not a matter of wiggling the wire, it's the twisting the wires and cracking the strands. Just spend the cash and change the harnesses

So does anyone have the cannon harnesses in stock?

PinBits usually does.
If it shows out of stock just email Pam

Cannon problems (Canon cannot find home)
1. Unplug 4 pin plug from underneath the play field (If you cant find the plug, follow the wires from the canon to under the play field and you will find it) , use a multimeter using the "tone" function, and test the MALE plug, back to the cannons transmitter opto. If you get no "Tone" to the transmitter opto you will need to replace the wires from the opto to the 4 pin plug.. if all is good go to step 2
2. Using a mobile phone camera on live view, look at the transmitter opto on the cannon, if the light is a very dim purple/blue you will need to replace the IR LED,(about 70c from a electronics shop). (This was the problem with my canon). If the IR Transmitter opto is bright go to step 3
3. Clean IR opto on the cannon using isopropyl alcohol, if its still not working. Put the pinball machine into test mode, and use the canon test to test the switches. if they didn't detect home (closed) you will most likely need to replace the micro switches or test the fuses
4. With the machine off, check the continuity of the coil harness - if bad replace whole harness

Good luck

this is normal, to the point where i wonder if it's a ROM bug. on mine, only one cannon rotates on bootup, but they've never malfunctioned during gameplay. i've seen both cannons rotate on boot up, but rarely.

I have a tng the problem your having is a switch, not the limit switch but the other that tells the ball not to shoot, I have had that issue before look at the switch with he test which cannon it is with them stowed they all should be closed. If it's not closed it won't rotate when turned on, Don't think it's a rom issue