Hey folks
I think I found the rear seat rattle problem. Mine is a 2014 RX 350. Beneath the rear center seat are 2 hinges which appear near the front of the seat. The left hinge is tight and snug while th right hinge has a little play in it.....very very little. But it's enough to get that rat-a-tat-tat metal to metal sound. I can reproduce the sound by hand by bouncing the seat or by shaking the hinge. The right hinge parts are a bad fit. But it is still intermittent while driving