Tailgate release only working off key - not handle
 

My boot release now only works off the remote key fob, if I press the button under the tailgate handle it does not release any more. This started as an intermittent problem but now is all the time.
I took the lower tailgate lock mechanism apart and found the spring had broke but checked and BMW only sell the complete mechanism. I purchased some springs and replaced it and it worked ok for a month or so but it's not working again.
Having taken the mechanism apart, I'm wondering as the actual mechanism works fine from the key if it might be a fault in the handle release button on the upper tailgate handle part. I have disconnected it from the car and checked for resistance on the connector terminals when the button is pressed and there is no resistance, so my basic knowledge tells me there is no connection being made when the release button is pressed.
Is my thinking flawed? Is it more likely still the mechanism spring or is there some way I can check 100% if the release button is working?

I see this is an old post, but having last month replaced my door actuators and having got back up to 3 out of 4 doors unlocking at the press of a button (yippee!), this month (perhaps hastened by the cold weather?) has brought the failure you describe.. (boo!)

It still unlocks from the (recently fixed) keyfob, but not the button on the upper half of the hatch.

Looks like I'll be buying a new switch panel.
I also noticed that the rattle I've noticed recently might be coming from my lower half of the tailgate, where only one side seems to 'latch'..

Ho hum..

Well,

After thinking I'd just ignore the problem, I was in the garage an heard the hatch whirring (not an accurate adjective) away as if the switch was pressed. When I took a look, it had 'released' and the trunk light was on. Obviously, not as easy to ignore a switch that thinks it's being pressed as a switch that doesn't work.

So I took it apart and the assembly was very wet and grimy. The gasket that seals the switch / handle / license plate lights assembly to the tailgate as shrunk and rotted, and allowed a lot of water in. The mechanism looked okay, and I think my problem was corrosion / bad connection at the electrical connector. I've cleaned it up and will see if it is temporarily fixed, while I order this gasket..

Gasket, trunk lid grip
This fits your 2000 BMW X5 3.0i
Part Number: 51137004531