This may not be the same as what you’re experiencing (location wise) but perhaps still of interest/helpful.
I have the refreshed S Long Range and initially heard zero noises on delivery. I was…Sooo contented (as I had a 2018S that has suspension click and creak noises and interior headliner noises that drove me insane, despite loving the car otherwise. They couldn’t remedy and I wound up giving back the 2018 to Tesla. I was wary when I purchased and picked up the 2021 Refreshed,
but love Tesla cars so much that I risked what was definitely and internal worry for me. On pick up…WOW…! So happy…
Scroll forward months and I started hearing a creaking sound. I think, dissimilar (?) to yours..my sound was emanating from the drivers rear seat area. Then…the same noise started happening on the passenger side. UGH!!!
Scroll forard, post service visit. They were able to fix this noise seemingly. Presently….I’m back to hearing nothing…which is ….ahhhhhh.
I’m REALLY hoping it stays this way, as I’m back to just..simply..loving the car.
They supposedly had to do something to/around the latching mechanism of the two rear seats. That made sense to me, as I had received recommendation on this online forum to wrap the latch mechanism with electrical tape (as a DIY fix).