You have to determine if it is a digit or a ribbon cable issue. Ribbon cable issues are usually noted by the fact that the same vane is malfunctioning across the board. Each digit is universal. Try moving the bad ones to a spot where the current one is working. Use program 11 with the toggle down to quickly make all the digits flash 88888 and blank. Bad digits can be easily replaced. PST stocks digits and ribbon cables.
DO NOT SPRAY THE DIGITS WITH ANY OIL OR WD40!!!
They do not need to be lubed!