Strange things happen during games: the DMD freezes while play continues, awards stop working, a ball is saved when it should not be, adjustment screens appear mid-game, or the display shows an impossible ball number.

Random glitches in play (DMD freezes, odd awards): reseat the ribbon cables

Cause: A poor connection on a ribbon cable between the boards. The boards themselves had just been serviced.

Checks

• Measure the 5 V at the CPU board and check its ground.
• Run switch and solenoid tests to rule out a switch fault.

Fix

• Power off and reseat the ribbon cables at both ends. Here that alone cured it for 40-50 games and counting.
• If glitches return, reseat the EPROMs and look for corroded chip legs.

Systems

• Data East CPU Version 3

Games

• Batman

Related tips

• Display EPROM version appears, then nothing more
• Batman: CPU and display EPROM types and latest versions
• Coil fires when grounded at the coil but not from the transistor tab
• Combining two-chip CPU code into one 27512 for 5C
• Odd DMD screens or "command 9c" errors with matching ROMs
• Game will not boot: GI on, little else happens
• Display shows "Command" numbers instead of animations
• Whole switch column dead after working under the playfield

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