The central locking system includes pressure/vacuum actuators that can be tested to either eliminate them and move on to an electrical problem causing failure in the central locking system.
The PSE(under the rear seat) has a distribution plug with the letters ABCDEF where A=left front door, B=right front door, C=left rear door, D=right rear door, E=filler neck flap and F=trunk lid
You would pull off the respective faulty yellow pneumatic line and place a 600 mbar pressure and a 300 mbar vacuum and hold for one minute to test the actuator for leakage, a 30mbar variant is acceptable.
If not in spec change the faulty central locking actuator.
If your door locks dont function you now have a diagnostic path to solve the problem