Charlie are you using shielded wire for the cable back to control box and is the sheild earthed just one end inside the control box.?
Also is the machine frame earthed to same earth point.?

You have long wire runs so they will act like antenna picking up any noise so you'll need to Eliminate this really before you'll get any joy.
I would also try a differant switch you maybe have poor switch with slow components giving slow reaction times.?