Before you respond, yes I’ve read the troubleshooting section on PinWiki and just finished seeing all of Clay’s repairs on -35 games. Now my problem with my Bally Fireball II

Squawk and Talk board a majority of the time has the LED only blink twice, (should be six total, I’m counting the ‘flicker’) and won't boot the rest of the way so no sound. 15% of the time it boots all the way with sound successfully. I have already-
•Replaced all electrolytic caps
•put pressure on and crimped the wires in the main connector further
•wire brushed and resoldered the male header pins
•checked that all test point voltages are still good even when the board doesn't boot successfully
•swapped the 2 PIA's on the board to see if I'd get a 3rd blink instead of just 2 on an unsuccessful boot, but it's still 2. (Game checks Speech PIA in U7 on the 3rd blink, then the same PIA used in U11 for the 4th blink, so if the PIA was sometimes bad it would make sense for the unsuccessful boots to change from 2 blinks to 3 blinks, but it’s always consistently at 2 when unsuccessful, and consistently makes it to 6 and works fine when successful.)
•Made sure the socket for blink 3 (PIA U7) was polished and perfect as well

where do I go next? I know nobody will probably have an answer but I am so damn stumped. Fireball II