Discovery 3 tail gate door.

[Richard Mills]

If you have a problem with the upper tailgate door, one of the items in the photo is to blame.
Item 1 is the push button, push it and nothing happens. The button itself is OK it's the zinc alluminium alloy
       lever that has turned to white dust. Maybe they should have made it out of plastic.

Item 2 is the latch mechanism, press the button, it gives a good klunk and the door only opens onto the safety catch.
       More pushes on the button gives similarly loud clukns but may nver open the door.
       It's that little hook on the end broken off.
Item 3 The actuator. press the button and get a weak clunk and it doesn't open the door,
       press again and the clunk gets weaker each time. But it might work properly the next day, just until you are
       in a hurry then it goes to sleep again.

The advice is, for any problem, change all three, it's a pain to get a stuck door open and you don't want to be doing it
time and time again.

[djkaosone]

If you have a LR3 or LR4, you should definitely do this mod to add a manual release lever to the existing electronic actuator. I've done it and works very well. https://expeditionportal.com/forum/threads/lr3-lr4-required-upgrade-prevent-rear-door-failure-for-25.159873/