Passenger front door lock won't unlock

I recently purchased a LR 2003 Disco II SE from a used car dealer. Has anyone had any problems with any of the locks, mainly front passenger door
lock not opening. I tried using the remote on the key and all the locks open except the passenger front door. The alarm system may be triggering this. I guess I will have to take back for check-up. I read manual but there was no reference to this type of problem. Any assistance is appreciated.
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Tom Jones fault i.e. "its not unusual " the actuator motors do stick 1st line of attack is WD40 into the lock mechanism and give the lock button a vigorous workout to free off any gunge mind you if its under warranty let the vendor have a play first. Derek (Kato's passenger door is locking intermittantly )
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Lock mechanism? Hmmm....where might that be? The passenger side front door luck that is stuck has no lock on the outside door handle. Another unusual nuance of the Land Rover Discovery II SE. Did I misunderstand?

door
triggering
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Just open the door and squirt the WD probe/straw thingy into depths of the' greasy ' bit of the mechanism which is then exposed, the object of the exercise is to clear out any gunge which is slowing the mechanism the vigorous manipulation of the button will help to clear it .Sometimes it works other times it may be necessary to remove the door card for access. Provided the actuator will either lock or unlock (currently Kato will unlock but the lock operation fails) then the motor is less likely to be at issue either way it is a very easy and inexpensive way of tackling the problem.
Derek
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I have appt next week with dealer who will take to his mechanic to attempt to repair lock. I may try your suggestion with WD40. Thanks Derek.

the'
unlock
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