My car has always been rattle free. I put down the drivers side section of the rear seat a week ago & ever since there is a rattle that seems to be coming from inside the folding seat back. There's a big plastic disc (silver dollar size) that goes through the carpet on the back of the seat. There sure doesn't seem like an easy way to open up the seat. Anyone else ever run into this? It seems like it's coming from inside the seat, if you tap on the carpet on the rear of the seat you can hear a little bit of a rattle.