In the test menu the flashers fire solenoids instead, though in play both seem fine.

Last Action Hero: flasher test fires coils instead

Cause: Cracked joints on the select (L/R) relay on the PPB board, or old CPU code.

Checks

• Inspect the relay's solder joints.

Fix

• Reflow the relay joints and install the latest CPU ROM.

Systems

• Data East/Sega CPU Version 3b

Games

• Last Action Hero

Related tips

• Jurassic Park, Last Action Hero, Tales from the Crypt: random resets in play
• Last Action Hero: CPU and display EPROM types and latest versions
• Jurassic Park, Last Action Hero, Tales from the Crypt: flipper dead from its EOS switch
• Jurassic Park, Last Action Hero: flipper return springs break
• Last Action Hero / Guns N' Roses: magnet dead or locked on
• Random coils firing and dead flashers on Tales from the Crypt
• Tales from the Crypt: random coils and dead flashers from a wrong K-1 relay
• Magnet driver MOSFETs on Last Action Hero and Guns N' Roses

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