2013 LEXUS RX 350 Suspension Problems

MY NEW 2013 LEXUS RX-350 MAKES A SIGNIFICANT AUDIBLE "CLUNKING" SOUND FROM THE REAR OF THE VEHICLE WHEN THE VEHICLE COMES TO A FIRM STOP AT EITHER LOW OR HIGH SPEEDS. THIS CLUNKING SOUND OCCURS WITH EVERY STOP FROM JUST A FEW MILES AN HOUR TO FASTER SPEEDS. LEXUS OF LAS VEGAS MAINTENANCE PERSONNEL HAVE LOOKED AT THE CAR AND CONFIRM THE "CLUNKING" SOUND IS FRAME/SUSPENSION RELATED AND IS NOT A LOOSE SPARE TIRE OR OTHER ISSUE. THEY INDICATE IT IS NOT A SAFETY ISSUE AND THERE IS NO FIX AS IT IS A PECULIARITY/DEFECT WITH ALL 2013 LEXUS RX-350 CARS. I PERSONALLY DROVE ANOTHER 2013 LEXUS RX-350 AT THE DEALERSHIP WHICH MAKE THE SAME CLUNKING SOUND FROM THE REAR OF THE VEHICLE. THE REPEATED "CLUNKING SOUND" IS IS DEFINITELY A VEHICLE DEFECT IN MY 2013 LEXUS RX-350. I AM NOT A SAFETY ENGINEER NOR WERE ANY OF THE LEXUS...