[RPI-M5]

I've had this problem for going on 5 months. 2 trips to the dealer haven't fixed it (BMW Seattle), and they are now backing into the "well, this is a high performance vehicle with a stiff suspension, so some creaking should be expected" dance. Trip #3 to the dealer is next week.

I tried applying the electrical tape last night, and it has greatly reduced the noise, but it is still there for only the most egregious situations where the rear end is in a "twisting" motion. Going to try applying more electrical tape to see if that helps solve it. I am worried the electrical tape is just a band-aid for a symptom and the real culprit is something very wrong with the structural rigidity of the car, or the tailgate coming very loose.

I've also noticed the plastic trim piece surrounding the latch on the bottom fold-up part of the tailgate to be very loose, and very noisy. Part of me thinks this is what is causing the noise once the loose tailgate rubs on it, or rattles on it. Anyone looked into this?

EDIT: I should mention what the dealer did each time I visited with this problem

Visit #1 - took apart trim in rear, checked rear suspension, lubricated and tightened everything there. Didn't touch tailgate. Didn't fix it
Visit #2 - cleaned and lubricated tailgate latch and attachments. Checked rear trunk cover (because for some reason, removing that made the problem go away) and found no issue with that. Tightened tailgate latch