This has been covered before. On my westy it would lock right after I
unlocked the door. The likely problem is a broken wire where the wire bundle
passes from the door to behind the dash. Many problems in my wiring came
from the wires being too short. There was so much movement and stretching
each time the door opened, wires broke from being bent back and forth. I
spliced in new wires to relieve the stress at the point  the wires pass
through the grommet/ wire cover between the door and the dash. The driver
side is most likely since it most used.