The second board I got from ekorz, or should I call him my friend after the gift he made to me.
Again board had colour issues:
Green was completely absent:
Going back from the JAMMA connector I quickly ended up on a cracked resistor on the final stage of the green colour amplification (33Ω SMD). I replaced it and colours were fixed:
I continued my tests and found left direction for player 1 wasn't registered:
Again starting at the JAMMA edge I found one of the custom resistor array (possibly containing capacitors too) stamped MLR8C4 IAM (or is it 1AM?) measured resistance between pin 2 and pin 3 was ~4kΩ when it should be 100kΩ. I pulled it but the lower resistance between pad 2 and pad 3 was still present. I was left with a single chip in line: a HCT244 (U42), I confirmed the ~4kΩ resistance between its pin 11 (input) and ground. Once replaced all controls were then working.