[Tony Van Helden]

when it is not working, and you put the code in the keypad outside, can you hear the solenoid latching?  if it is still making the clacking noise, then it is likely from the door open button inward.  if it doesnt, then from the keypad inward to that control box.  

the control box for all that is in that cabinet just inside the door on the left down at floor level.  make sure there are no loose wires there.  

tom