Is there a youtube video on how to get those panels off? I know next to nothing about cars and don't want to damage anything.I had that in mine and it came back. Mine was more predominant when I hit a slight bump.
First time, it was loose bolts in the inner fender well in the back. Another person fixed his by tightening those after I told him that.
You might check them...
If not that, there are modules near the subwoofer that also rattle loose. Mine weren't 'even finger tight' on a passenger control module, I believe.