92 300SD door lock issue

[Basstrip]

For some reason my driver door lock does not work property. When I unlock/lock the car from the pass door or the trunk, the driver door does not unlock/lock, but when I unlock/lock the car from the driver side, all doors unlock or lock. I don,t have an explanation, if I have a vac leak at the driver door, wouldn't the door will be have problems with locking and unlocking with the key at the driver side? I do not have the remote for keyless entry, I use the key at all time.