Your recording sounds pretty much the same as my NX300h 2016. I've had it for 3 weeks and love it...except for the creaking sounds in the back. Sounds mechanical and is sometimes sounding together with control arms over speed bumps. Primarily seems to happen from side to side warping of the car body. I feel it originates somewhere between hatch and tailgate. There are no signs of panels rubbing against eachother, i silicon sprayed the door rubbers. Moved all the clutter from the hidden storage hole (no spare tire, just a repair kit). Pushed and wiggled evere panel in the back, shook the car side tot side, pushed down on the tailgate....no creak, squeak or moan. I cut of the lip of the rubber floormat so it wouldn't touch the hatch trim, i screwed it down so it wouldnt slowly creap up against it during a drive. The mat has been excused as a suspect. cargo in the hidden storage too.
Still... every time; it might start to creak from the start, or when i drive back home from work. It doesn't seem to be temperature or humidity related.
I guess i am going to have to unscrew all of the trim and buy some felt tape. I can live with the occasional squeak and creak form the suspension when taking a speed bump too fast, but this creaking is too much for me. Kind of sounds like there's a huge amount of torsion in the tail gate and one or two body panels havent been welded together.