I came across this old post as I am now a FF owner and had lots of phantom goals. What I did to solve the problem was to unplug the bank of optos by the goal.

After I lifted the playfield, there is a red connector on the left and after unplugging it, the opto in the subway was still working so the game plays great. There is a slight delay when you get the ball past the "goalie" and you will get beaten by the halftime/final buzzer in some instances. Regardless, this did the trick and I think it'll work for you as long as your opto in the subway is working fine.

I saw in another thread that someone was talking to the ColorDMD guys about this. Would be nice to have ColorDMD support and this game has amazing dots!