After a pop bumper is hit, its relay stays pulled in and the score reel stays energized.

Gottlieb pop bumper relay and score reel stuck on

Cause: The pop relay holds itself in, scores, rings the bell or steps the 00-90 unit, and fires the bumper coil; the coil's normally closed end-of-stroke switch opening is what releases the relay. If the EOS switch is bad, or the relay's heavy coil-power contact is dirty or gapped too wide (so the bumper coil never fires and never opens the EOS), the relay never lets go.

Checks

• Clean and check the pop bumper EOS switch.
• Check the large contact on the pop relay that feeds the bumper coil.

Fix

• Clean and set the gap on both switches.

Systems

• Electro-mechanical

Related tips

• Pop bumper stays on after the ball hits it
• How an EM pop bumper works
• Rebuilding an EM pop bumper
• Pop bumper armature links: which to use and how they go together
• Making pop bumpers kick harder
• Cleaning and adjusting the pop bumper spoon switch
• Strengthening pop bumpers by removing coil windings
• Renew sleeves on flipper, pop bumper and sling coils

Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part Two, Clay Harrell (pinrepair.com)