S.Carolina plant workers (and their robots) had their hands growing out of their asses, seriously.
In an effort to relieve the random clunk somewhere in the back of the vehicle, I decided to pay close attention to upper and lower tailgate, since someone on this thread mentioned it helped remove the clunk after readjusting.

I was amazed how misaligned the lower tailgate was - in all dimensions. Lower half of the lower tailgate was pushed forward, while upper half sticked bak out. At the same time, the tailgate was sitting too low vertically, resulting in ridges of the body being misaligned with ridges of the tailgate.

After alighning, the clunk seems to have stopped (knock on wood :)).
The ridges are alighed and light doesn't break, which helps the overall look.

Here are some before and after pictures. I dont think there's a need to label them..

Wow! Job well done! Any tips before someone tackles the job as well or just trial and error?

Thanks.

Yes, I had to go low-tech way to fix the lower tailgate being too low vertically, and thus misaligned with body.

I have looked carefully, and there's no other way to lift the tailgate but to insert a 1-mm spacer (washer cut in half) as in the picture.
It props up the taigate nicely. The spacer can be adjusted as needed - pushing it in further will prop tailgate higher.

The picture is showing how to adjust bottom half of lower tailgate inward and outward. My vehicle had the bottom portion misaligned (sticking out too much). The adjustment had to be done a few times, as the top portion of lower tailgate has to be adjusted inward/outward as well. Pushing the top portion inward too much results in bottom portion coming out outward. You would have to balance them to move the whole tailgate inward or outward.

After adjusting, the tailgate does not need to be slammed to be closed, as had to be done before. Left and right locks close almost simultaneously with a push.

P.S. I wonder how many people have their tailgates misaligned. Post pictures :)

I've had soooooo many rattles in the rear trunk. Have fixed them all after 3years. I should be working for BMW. We should all get together and sue BMW. Every e70 has trunk rattle issues at some stage in their life. It's. Design fault.

I have read people on this forum mention that switching to non RFT tires relieved many rattles. Also Adaptive Drive does the same.

While I think there are some design issues, the rattles occur due to stiff suspension and most of all, the dreaded RFTs.. Just too much shaking and vibration that otherwise gets absorbed by normal tires/suspension.

Thanks for your advice. Absolutely makes sense. I'm waiting until my tires wear off and then to normal tires. Also I'm not a fan of low profile tires for this reason, I'm on stock standard 18"

bringing this thread back from the dead. I am still trying to tackle squeaks and rattles throughout my x5 and came across this site that may help some of you solve some of your issues.

I am having occasional plastic type creaking noises coming - JustAnswer

and pics to remove rear trim around hatch window
BMW TIS - 51 49 002 Removing and installing/replacing panel for rear window frame (compact)

Rear Cargo area retractable cover was causing my rattle. Had to remove it and store it. Also, dealer fixed all plastic according to the technical service bulletin with felt. No more plastic squeaks or rattles coming from the rear.