I have had a noise issue with a 25’ GX550 for the last couple of months. It sounds like a metal ticking or rattle noise from the rear passenger side around b-pillar area. I also noticed that it becomes louder and more frequent at higher temperature.
Welcome to the club... mine's in the passenger C pillar. It's a known issue with the spot welding of the body panels. Took 3 visits to the dealer and they installed a "wedge kit". That seemed to silence it for about 6 months, now it's back. Going to give the dealer one last shot before I pull everything apart myself and apply structural adhesive to the body panels.