TC,

Do you have to pull up the latch inside the doors "up" while someone
pulls the door handle open to open the door? or LH Front passenger door
use key to raise inside latch couple of mm then open door with handle?
If so there is a small spring in the door lock mechanism which is broken.
My central locking works OK lifts inside buttons up, but because door springs are broken they drop couple of mm enough for the lock to engage again.
I've had springs go on drivers, front passenger,rear passenger and rear door go on my Disco S1. Common problem so I hear.
We were able to get replacement springs from local Landrover repairer who had them made up especally as normal alternative is replacement of door lock at some ridiculous price from LR dealers.
Note springs on passenger doors are diffrent to drivers side doors and rear door.
I'm still waiting for LH Sides to be manufactured and have to lean over and pull button up for misses or let widow down for her to do herself

I will try Cobra's Idea on bending the rod and see if that fixes the problem

Cheers

Baggy