A small repair.
Game works fine except button 2 (jump) is unresponsive.
Some resistors arrays have burnt marks and the concerned trace coming from the JAMMA edge is burnt too. Clearly the board has been plugged backward.
Unfortunately those resistor arrays aren't standard and I don't have any spare part. So I did a small hack for this input by using a 10k resistor for pull-up and patching the burnt trace with a piece of kynar wire:
I don't like that kind of ugly repair but well, it works.