> I really do need to look up more about this daughter board thing.
There's nothing to look up. Unless you have the actual arcade and can start unplugging PCBs to see which one triggers the error
The daughter board error doesn't affect anything. If I had to guess, "daughter board" refers to either the MPEG sound board or the motor (force feedback) drive board. Likewise for the "one processor detected" message that some games display (Fighting Vipers 2).
But as RB said, nobody has actually bothered to look into it.