Ford Fiesta LX 2003 Door Locking Problem?

I have a ford fiesta lx (2003) 5dr

The central locking isn't working on the front passenger side with the key. When the passenger side is pressed in it locks all the doors as it should. When i press the driver side it locks all but the passenger side. The FOB locks all the doors except the passenger side.

Any ideas?

Obvious - there's a fault in the central locking system. You will need to plug in a diagnostic computer programme to identify the exact problem. Which means it needs to go to a Ford dealer.