OK if there isn't a L/B then it has to be the power the to the other door locks. The switching process is a two stage affair, first the drivers door is unlocked, this operates a switch (K2-01 below) that triggers the switching of door lock module (K2-02) so that the other three door locks are powered (K2-03/04/05);

Given that the locks are "twitching" -
I presume ALL three locks are twitching ???
- then the drivers door switch K2-01 must be operating, after that the fault could be;
In the switching module,
Power to the switching module,
The easiest thing to check first is the 30 Amp fuse to power the module fuse X03-5;

remove it clean the blades.
Next will be to check the plug to the module K2-02, unplug it and then remake the connections, its on the bulkhead behind the glove compartment (remove to gain easier access).
If the fault persists then it could be down to the relay inside the module itself, I've not had one to open up and see how practical that is but it would be my first move, otherwise replace the whole module.