Player 1's hundreds score reel works only some of the time, while player 2's hundreds reel always works.

Player 1 hundreds reel steps only sometimes: dirty contact on the player 2 relay

Cause: A slightly dirty switch contact on the player 2 relay, which routes power to the correct player's reels, was not passing power to the player 1 hundreds reel. A loose wire on the reel's own EOS switch turned out not to be the cause.

Checks

• Use the schematic to follow the hundreds-point circuit from the scoring relay through the player relay contacts to each player's reel.
• Compare the switch states on each score reel and relay at rest; ask before reattaching any loose wire that buzzes when tried.

Fix

• Clean (and adjust if needed) the contacts on the player relay that feed the player 1 hundreds reel.

EM games run some circuits at line voltage; unplug the game before cleaning contacts.

Systems

• Electro-mechanical

Games

• Flicker

Related tips

• Every hundred-point score also adds a thousand
• Clean the score reel relays
• Bally score reel relays
• Reset stalls with the player unit stuck at step 20: broken wire to a score reel
• 1000-point relay, ball index and chime lock on: dirty score motor switch
• Hundreds score reel won't advance though the bell rings: relay switch gap too wide
• Players 3 and 4 reset but players 1 and 2 never do at game start
• Score reels by maker

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