A strange one here, iv noticed that one bank on the left it only workes proper if they fall bottom middle top, if they fall any other combination it takes about 5 seconds to register. The fault is on the drop target board itself and i have tried changing the lm339 chip but still the same, could it be a faulty opto although it works fine if they fall in order? Iv noticed the board at fault is slightly different from the others but im sure its not had that fault all the time iv had it. Any help?