After about 20 minutes of play the game gets stuck in a loop, playing the coin-up sound and adding credits and points. Hitting certain switches knocks it out of the loop. Switch test looks normal and it doesn't happen from a cold start.

After a while the game loops awarding credits and points: shorted shooter lane switch

Cause: A shooter lane switch that shorted once the game warmed up. Switches with a small capacitor across them are worth checking first.

Checks

• When it misbehaves, unplug the switch return connector at the CPU (CN10 here); if the looping stops, the fault is in the playfield switch wiring.
• Look at the switches involved for shorted capacitors, touching blades or wires that short when warm.

Fix

• Repair or replace the shorted shooter lane switch (or its capacitor).

Systems

• Data East CPU Version 1/2

Games

• Laser War

Source: Pinball Repair help group!! (Facebook group)