rear door lock

my freelander 2litre back door keeps opening when driveing, when i lock it at night with central locking it buzzes,opens ok, the window drops ok and you can open and shut no problem but when it opens while driveing window does not drop, checked everything electrical so will it be the actual lock or something else,if i put indicaters on while driveing a buzzing noise from door, any ideas,thanks

Solenoid in rear door needs replacing, you can try lube if you strip it down but they Re not expensive new