Front passenger door central locking issue

Hi Folks, I have a 2012 Prestige Model - can anyone offer some clues as to why when I open the car via the keyfob or keyless entry on the driver side door all the doors open apart from the front passenger - someone has to climb over and open it manually from the inside - problem seems to be intermittent

The door solenoid module will need replacing, it's a common fault and relatively easy too.