The game came with a two-prong (ungrounded) line cord, and you may feel a tingle when touching the lockdown bar or side rail and another game at the same time.

Game has a two-prong power cord: fit a grounded three-prong cord

Cause: Without the ground pin, the cabinet metal is not tied to earth ground, so leakage voltage can sit on the metal parts.

Checks

• Unplug the game and inspect the cord's condition.
• With a grounded cord fitted, check for continuity from the ground pin to the ground strap, side rails, legs and lockdown bar.
• Confirm the line fuse is the correct value.

Fix

• Replace the cord with a proper three-prong grounded cord and connect its ground wire to the cabinet ground.
• Do not tie ground to neutral.

This is line voltage work. Unplug the game before working on the cord, and have the wiring checked if you are unsure.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

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