Quoted from jonnyqtrek:
I actually experienced it quite a bit on Williams... The ball would be sitting on the flipper, then I'd hear what sounded like a construction vehicle shifting gears, and the ball would hop around on the flipper like a pat of cold butter on a hot stove. Took a while to figure out that ghost nudging was what was happening. At this point, I've just decided to convince myself that the ball is sentient and gets bored staying still.
Man, shoot a message to A1Up. It seems like a massive number of their original models came out with bad g-sensors. To test the g-sensor, and you need to use the stock coding to do this, have the machine off and hold the left white button on the front of the cab, the launch button, and right flipper button, then turn the machine on while still holding the buttons in. Keep the buttons held down until a new screen pops up. You'll push the launch button a number of times to go through various tests and then it will bring up a screen with a green circle on the left, which is your accelerometer. Just stand there for a bit without touching the machine and see if your green circle goes red every few seconds. If so, then you've got an issue with that g-sensor.