There has been an intensive discussion and usability testing of different options during the 2.7.x beta about the influence of the door sensor on some functions and the joint conclusion was that for Lock’n’go the door should be locked in any case, even when the door sensor reports open or disturbed.
See:
In your case either Auto-Lock or a Keypad (locking via back button) are probably better choices than using lock’n’go.