2008 XF SV8. The keyless locking and unlocking does not work on the driver's door unless I am holding the key in the hand that I use to unlock or push the lock button- i.e. the range is extremely small; if I press the lock button without the key in the same hand I get the double beep, if I go to open the door without the key in the same hand it does not unlock. All other doors work fine. New battery in fob makes no difference. What might the fault be with this one door lock? A broken wire or something?