central locking on my hyundai terracan has a mind of its own??

my central locking on my terracan is mad, i changed the battery in the key fob? not made any difference.i can unlock it by useing the key in the door but straight away it locks its self up again on its own,i must have a gremlin in the car!!. i changed the fuse no fault found, if i sit in car with the key in the ignition but the door not locked and i take out the key the doors automatically lock themseleves. can any one help??.