During play the game abruptly ends with what sounds and looks like a slam tilt, without the usual reboot.

Game suddenly ends mid-ball: false slam tilt from a matrix fault

Cause: A switch-matrix fault makes the CPU see the slam tilt closed. Here one playfield switch was stuck on because its diode had been crushed across the switch lugs, and two switch plugs under the playfield had been swapped.

Checks

• Run switch test and look for any switch that shows as permanently closed.
• Inspect the diodes on playfield switches for damage or shorts, especially near the stuck switch.
• Check that the small switch plugs under the playfield are on the right switches.
• Check both slam tilt switches (coin door and cabinet floor) are not stuck or set too sensitive.

Fix

• Replace the damaged switch diode so it no longer shorts the switch.
• Put any swapped switch plugs back in their correct places.
• Re-test with several games.

Systems

• WPC Alpha-Numeric

Games

• Funhouse

Related tips

• Hallway multiball and Frenzy start on their own: one bad switch diode on row 5
• A dedicated (direct) switch does not work
• Game keeps resetting during play: poor J101/J102 power connections
• Eight switch matrix fault patterns and what they mean
• Sound suddenly goes haywire: reseat the sound ribbon cable first
• Narrowing a switch matrix fault to the CPU board, wiring or opto boards
• "Slam tilt stuck closed" at power-on
• Matrix fault remains with a good CPU board

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