I'm guessing that this happens on all 5 displays?? If so have a look at J1 on the MPU board, in particular pins 25 thru to 28, (these are the display segment data lines).
Check for a dry solder joint on the mpu J1 pins maybe.. or more likely check the connector pins inside the plastic connector housing and the MPU board pins for corroded or tarnished pins.
Might be time to repin some connectors!
Hope this helps!! Cheers... Mitch
