Today, our family is in the car, heading out to lunch. Two adults in the front and two teenagers in the back. When we come out from eating lunch, there is a plastic piece (see image) laying in the back seat, and the teen who sat in the other seat can't buckle his seatbelt (it won't let the metal buckle go all the way in, as though the seatbelt thinks it's already locked).

There's no obvious problem with the seatbelt...the latch release presses in and springs back up, it just won't allow the latch to go in.

We're scratching our heads over this. The car is a 2013 Volvo, purchased in April last year, so still pretty new to us. When we bought it, one of the latches to fold the rear seat down was broken, but that was the only issue. It's been a great car so far, but this has us scratching our heads.