Is it the vibration of the flippers causing the G.I to flicker?
Either way, I'd remove the driver board and with a DMM check the G.I traces from the plug to upstream components. I would also check the underside of the header pins for cold joints.
Secondly I would check the G.I plug which goes into the transformer (yellow/white & yellow) and reseat the connector a couple of times. (with power off and unplugged of course).
Is it ALL G.I doing the same thing or certain strings?
+1
And look closely at the connectors for GI - From memory - J120 + J121 - just in case they are a little brown.
