Central Locking Issue

[curlyearly]

My doors lock properly using the switch located by the window switches on the drivers door.

However with the key in the drivers door or using the alarm remote control, I can only unlock the doors and not lock. The alarm does arm however using the blip.

Any ideas on what can be wrong?

 

[gotmud]

PDL actuator may have gone south on you. How long has it been acting up?