On a game that sat unused for a while, two-ball multiball never ends: drained balls are saved over and over. Single-ball play and three-ball multiball (down to two balls) behave the same way.

Multiball never ends because every ball is saved: try a factory reset

Cause: Corrupted or odd settings in the game's memory; the trough switches and ball count were fine.

Checks

• Confirm the correct number of balls is installed and every trough switch works in switch test, alone and together.

Fix

• Do a factory reset (master clear) from the menus, then set the game up again.

Systems

• Data East CPU Version 3

Games

• Jurassic Park

Related tips

• Display EPROM version appears, then nothing more
• T-Rex never eats the ball though the setting is on: head not centred on its switch
• Game locks up or behaves strangely, worst in multiball

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