I have a 2014 GS 300h since 2015 and like you guys can hear this intermittent screeching noise. I'm sure it's coming from the rear wheel on passenger side. I have had it back with Lexus Ireland and they suggested that it was the brakes due to constant light brake use .... And suggested some regular hard brake activity... But as they couldn't replicate the problem they can only recommend and suggest. I've done the hard braking but the screeching continues.
Anyone with any idea as to what is generating this noise.