Sachsi

I've been noticing an intermittent rattle from the second row of our Q7.
It's happening more often lately and it was definitely not there when the car was newer (1 y/o at the moment).
It doesn't happen all the time (it seems to be temperature/humidity-dependent) and when it does it does not seem to be affected by the seat's position or load.

I assumed it was some seat latch, as described by several other members here but it turns out it likely is the back door panels. If a passenger in the rear seat presses hard enough against the top plastic panel (say at a 45 deg angle) the rattle stops.
Either the plastic panel or something underneath knocks against the door body under certain conditions (on hot days for instance) and it drives me nuts.

Have any of you experienced the same and is there a simple fix?
TIA!