Have you done any work on the game recently?

If you replaced a switch, mis-wired lugs could be your answer.

If it's not what Pam suggested, it's probably a similar easy fix--you just have to find it by scouring every square inch of the game (also check the matrix like Taylor suggested).

Then look for things like something shorting the point blades on switches.

A wiring short (also check the door harness).

Switch lugs, wires, diodes all smashed together and shorting out.

Perhaps even something like a fallen screw behind a board (lower cabinet or head).

Good luck with the hunt.