well i have a jeep and the back door rattles like no other...i took off the back door pannel and checked out the situation and ...the rattle..is from the door hatch..
i dno about your door, bu ton mine, that was really the only moveable part.
along with the license plate
i found some of that white packing material in my basement, the stuff that comes in sheets...about 1/3 cm thick...i put that all behind my license plate..that took care of that.
then i packed it all around the door hatch....inside the actual door, under the door pannel.
it helped with rattling, but it in no way is sound deadning ..
my trunk that latches is on the very bottom of the floor, because i push a button and it lifts up... but is sounds like it is coming from the panel maybe. hmmmm