Are you able to adjust the rear, outside headrests? It seems as if they are locked in a fixed position and you are not able to slide them up or down. The manual only shows that the front and rear center headrests can be adjusted but does not mention anything about the rear outside ones, besides pushing them forward so that you can lower the seats. There is a little button on the left hand side of each headrest that seems to release only that side, but the other side is still locked, which keeps you from being able to move it up or down.