Not too sure but if yours is a modern veh. then I wouldn`t be surprised if the alarm is operated through your central locking/door lock assy and also through an ecu,it sounds like it is sensing the actual lock is open but the door is actually closed,I don`t know what the workshop have actually done or what parts have been tested and would have thought any door contacts have been checked out but have you thought about trying a replacement lock/catch assy,if you try and see if there is wiring to it,a second hand/used from a scrappy may be worth a go.That is only an option,it may have been tried already,good luck.
cdc, August 2013
