Flippers work at first, then fail entirely.

Flippers work for a few minutes then stop

Cause: Cold joints or worn contacts on flipper enable relay RY1.

Checks

• Inspect RY1's solder joints and contacts.

Fix

• Reflow or replace RY1.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• CPU board flipper relay RY1
• CPU flipper enable relay RY1
• Flippers never work: flipper relay RY1 not pulling in
• Check every coil's resistance before first power-up
• Flippers and special coils all dead
• Monday Night Football: switch column transistor Q54 keeps failing
• Whole switch column dead after working under the playfield
• Pressing one switch closes the whole row: bad 4011 chip on the CPU board

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)