I know this is a bit of an older post but wanted to check back in anyway to see how the resolution went. We have a 2013 Model S, air suspension, 113K, and I have a very similar issue. I had Renton look at at and they replaced the front suspension aft links (both). Didn't help. I then did the sway bar links myself as you did. Didn't help. I'm planning to hit up Bellevue for the next assessment as Renton doesn't seem to have the right expertise here. So, curious to if you ended up with an upper control arm replacement, a strut(?) replacement, etc. Our knock isn't a squeak, it's a good ole single clunk typically when reversing slowly, especially when the wheel is turned to the right. Does happen in forward over small bumps but is really pronounced when reversing out of our garage and it does it on an ever-so-slight elevation change. Appreciate any info (if you're still online).