Weird door lock/handle behaviour

[HPsauce]

One of my doors, nearside rear, is very rarely used. Mainly when I want to plug in my tyre pump to the cigar socket.
I fully unlock the car with the remote, open the boot and take out the pump, reach for the NSR door handle and pull it. Door stays shut with the lock button clearly already raised.
Release handle and pull again, door opens normally. If I then close up, lock the car and unlock the door opens first time.

Anyone have any idea why, is this a "problem waiting to happen" or "just one of those things"?
It's only that door and only if left for some time, probably days.

[Ronin]

Its due to age & lack of use. slowly getting seized with rust. same thing happened on Dean's yellow turd.

[MikkiJayne]

Yeah exactly ^ The problem is the catch itself siezes up in the housing due to either the grease getting hard and gumming it up, or corrosion inside the plastic-coated metal parts expanding them so they don't move freely any more. Several of mine do the same thing.

Its usually possible at this stage to save the lock by dismantling it, degreasing thoroughly, and then regreasing with lithium spray grease. Sometimes they need soaking in evaporust too although watch out for the microswitch / central locking pod.