Rear door won’t unlock

This summer I dismantled the rear door mechanism as the central locking didn’t work properly at the rear right side. I greased the mechanism and cleaned the electric connectors. It worked fine for a while.
But suddenly the rear right door won’t unlock – the mechanism moves together with the rest of the locks but returns immediately to locked position while the other locks are open. Resetting the locks by disconnecting the battery and synchronize all locks doesn’t help.
Can anyone help me with this issue?
Have I missed any guide line or trick to overcome the problem?

Sounds like the mechanism is sticky, I think you are going to have to get in the back and when the lock is activated grab the plunger and stop it from retracting, then get into the door and lubricate the linkages.

Johan, I don’t know the model year of your XJ40 (you might want to add that to your profile) but my '94 had an issue like this when the linkage adjustment was off just a tad. The lock would work fine when the temps were warm but when cool temps took over the left rear door lock would not cooperate. When warmer weather returned the lock worked properly. When the shop that did a strip-to-bare-metal repaint of my car a couple of years ago removed and replaced the outside door handles the linkages were adjusted and the lock has behaved properly since. So along with the lubrication I would try adjusting the linkage.

Thanks Mike. Its a MY -92 Daimler version.
Your advice sounds right. I will look into this and adjust the linkage.

Hi Robin - right now it is in winter sleep but I will try your trick asap.