Search:

Has it got a key lock on the tailgate as well if so disconnect the central locking off the tail gate and manually lock unlock

Put it back in? Probably a connection or a servo, take the back tail gate to bits and check, either there or the drivers door switch?/ connection

Shoulda bought a Great Wall Happy?

aaahhh Self locking cars, they just shit you to death. My last two every time i walked away they locked themselves. Unlock from the kitchen and head to the car to get something and Murphys says sorry...