S205 C63S estate squeak and boot trim removal

[minsAMG]

My 2020 S205 has developed an irritating squeak that I have narrowed down to something behind the N/S boot trim just behind the rear seat under the 3/4 panel window (circled in red). If I push on it I can replicate the squeak. More interestingly, as I park the car with the handbrake off, when i thump this area with my fist, the electronic handbrake activates!
I suspect there are electronics or some kind of sensor hidden in there.
What I cannot work out is how to remove this carpeted trim as the buckle for the folding seat back prevents me pulling the panel off. I would really appreciate it if someone can guide me or advise me about what is behind the panel and how to remove it. A parts diagram for the area would be great.

 

[TrueSpirit]

Very interesting a couple weeks ago I test drove an e63s estate and there was a rattle (rather than squeek) from the rear and I thought it was the removable and retractable boot lip piece. Definitely when I agitated and shook that piece, it rattled like when I was driving it, but it seems like your squeek is from behind that trim piece, I don't know anything about what hides behind there! Sorry

 

[minsAMG]

When I press on the red area, it squeaks and when i thump it lightly, the EPC engages. I would now love to know what is hiding there, and fix the squeak in the process.

 

[Petrol Pete]

http://mb-teilekatalog.info/view_GroupAction.php?lang=E&mode=BM&class=1&aggtyp=FG&catalog=69P&model=203276&spmno=0&group=82

Enter your car in here .

 

[minsAMG]

Thank you! That's really helpful. It appears it's the Keyless Go and 360 degree camera computers there.