[Varinn]

Don't take a diagnosis from a random dude on the internet as gospel regarding a sound you can only describe with words :P

If you can't verify it, it's best to check it out however you can. Pop the hatch and do the bounce test yourself. If it's inside the car it should be pretty easy to single it out, I believe RSM's are an item that are good to replace early in their failure state cause I'd imagine that a catastrophic failure of one would let the shock potentially punch right up and inside the car (someone could correct this if it's not true)