A switch that is on the same row or column as the outhole switch is likely has a bad diode, and when it closes, registers as the outhole. Look on the schematic for those switches, put the game in self-test and let all three balls kickout to the shooter-lane, and then put it in switch-test. At that point, when you hit one of the identified (same-row or -column) switches, you will hopefully identify which switch is mis-identifying as the outhole.