Erratic Left Rear Tire Height, Dealer Can't Figure It Out, Pls Hel

[Cachimaru]

Hi All, I'm new to the forums and would love some help. My loaded '04 RX330 has 190k and it's been a tank for me. Best car I ever owned by far. Recently the left rear wheel height has been fluctuating: sometimes riding higher than the other tires, sometimes lower, sometimes the same. No indicator lights comes on and the car runs perfectly normally otherwise, except for not absorbing bumps and potholes as nicely when the wheel height is off. It must look funny from behind, though. Both the Manhattan and South Hampton Lexus dealers have 'fixed' the problem according to what the computer tells them, but since the REAL problem isn't telling the computer that something is wrong, there is no way to fix it, even though the car clearly has a problem when you look at it. I literally can't afford to have the dealers throw darts at the problem until it's fixed...10k later. So, I'd love any thoughts on how to proceed and perhaps if there is a reputable independent Lexus mechanic in the Long Island/Hamptons area who actually figures out problems like mechanics used to do, I'd love to know about him. Picture shows car slightly slanting downward to left while parked.

Thanks in advance for any advice.