P38A Rear Door Lock not locking

Guys,
My rear offside door has stopped locking properly on the central locking. Unlock works perfectly. It seems the lock motor is working in both directions, but does not pull the button down fully.

If I lock the door using the button, and then lock the rest of the car with Fob, then all doors are locked properly. Unlock pops all the buttons up ok again.

Any ideas before I start stripping the door ?

Pete

Grease gone hard maybe.

So yesterday prepared to take the door part & investigate. Lo and behold, the door is now looking again properly. It fixed itself.

I suspect the "grease gone hard" maybe correct, & warmer day sorted it !! Time will tell.