TD5 Door lock and alarm issue

Hi all, any help with this issue would be very much welcomed by my neighbours! My Defender 90 TD5 door locks open with the key fob but then within 1 or 2 seconds the doors seem to lock again while I'm opening the door. I'm left closing the door before the alarm goes off then opening the door with the key but the alarm then goes off anyway. Anyone had this issue or can advise me on resolving it before I get lynched by everyone on my street?