Blind guess #1. Someone over fused the flasher circuit(s) in order to bypass a problem with the PPB or driver board. Not certain where the flasher fuses are located but there should be at least 2 if some signals come from the PPB and some come from the main driver board. I know there are multiple fuses on the PPB and I think that each fuse covers multiple connections on that board.
I swear that EVERY single Data East machine I have ever owned (I've had around 10) ALWAYS has the wrong fuses in it. ALWAYS.
Once you confirm all fuse are the correct value, if one or more do blow, that will point you in a better direction.