Central locking problem on Ford Focus 2002?

Hi, I just purchased a Ford Focus 2002 today. The passenger door was replaced and now the central locking system does not work. If all doors are closed and you press the button on keyfob to lock doors it clicks twice, locks and opens doors again. If you lock the passenger door from inside the car, then exit car, close all doors and then press button on keyfob it locks car fine. How can I correct this so all doors lock with keyfob?
Thanks.