I stumbled upon a possible fix in another x forum. If you have the rear cargo cover in the extended position, the cargo shade edge that run along the right and left sides of the trunk space tap on the track where the shade follows the track, the noise appears. The fix is to install a foam strip or gasket of some sort, along the bottom edge of the track.

I haven't tried retracting mine so the cargo space is open. I've been driving around with the shade in the extended position and started noticing the noise. Today, I was planning to retract the shade to see if the problem disappeared but I completely forgot about doing so until I heard the noise again just as I was pulling into my street after work when I got home. I'll have to try tomorrow.

Scroll down to Post # 4 if you click <here> to go to the other forum where I found a solution. There's a photo of the area I'm referring to. Maybe this is what's causing the OPs issue here?

Good luck!!