CODE INPUT and the DRIVE CODE setting allows you to set a security feature on the unit whereby you can specify that when keyed on, it has to see either a fwd/rev or steer input every time before it will allow operation. Setting it back to factory defaults will set the DRIVE CODE function back to disabled. Either you were unknowingly hitting the correct input 10% of the time after key-on or one of the pots is not correctly adjusted and the controller was seeing it as a code input occasionally.