At game start the ball count resets to 3 and a chime rings (the special may light), then the count drops to 2 before the ball is served to the shooter lane. The ball count unit itself is clean and steps normally.

Ball count drops by one as the first ball is served: stuck 10-point playfield switch

Cause: A playfield switch in the 10-point circuit was stuck closed, so the game started scoring before the ball was in play. Because the outhole switch was still closed at that moment, the game took that as the ball ending and stepped the count down. A separate wire had also come off the eject advance unit, which affected the special.

Checks

• Listen and watch at game start: a chime or reel step before the ball is plunged means a scoring switch is closed.
• Note which reel or chime fires (10, 100 or 1000) and check every playfield switch in that circuit, and the scoring relays, for one stuck closed.
• Check the ball index relay stays at rest until points are scored.

Fix

• Free and re-gap the stuck 10-point switch.
• Resolder the loose wire on the eject advance unit.

EM games have line-voltage circuits: unplug the game before working on switches and units.

Systems

• Electro-mechanical

Games

• Triple Strike

Related tips

• Ball-in-play and game-over lights all dead: bent switch blade on the O relay
• Wrong player comes up on ball 2 and scores won't reset: stuck P relay switch
• Rollover advance unit won't go back to 1 on reset: weak return spring
• Ball count stays at 1 after each drain: dirty secondary trough switch
• Score motor keeps running at start and the game never starts: clean the ball count unit
• Players, credits or ball count not resetting points to a stepper unit
• Game starts but flippers are dead and nothing scores: dirty relay switches
• Game Over relay trips again right after start: dirty Lock relay switch

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