Our car used to do that if a door or boot wasn't closed properly,spray the mechanism's they might not actually be locking in the firrst place.
a
October 2016
The problem may be a slightly seized locking mechanism in a front door,probably the passenger side if it isn't used much,there is a pin on the outer handle which is prone to seizing and the door card needs removing for access,another check could be the wiring between the door and door pillar,worth a look, good luck.
cdc
October 2016
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