I got my (2018 showroom inventory model) Model S less than two weeks ago and just had my driver door handle fail. At first it wouldn't let me close the door (instantly unlatched) as the handle sensor seemed to think I was trying to open it. I was able to get the door to close by pressing the lock button on the touch screen then closing the door (I believe this makes the car ignore the user trying to open the door). It's been working on and off, but currently it extends correctly but pulling it does nothing and it doesn't fully retract without me pushing it in. Thankfully I already had a service appointment tomorrow to get my tire that came with a tear replaced, so they should take care of it then.
My car (279xxx) was built in September 2018 and was pulled from the showroom in late March. I'm not sure when it went into service as a showroom model, but it had 450 miles on it when I got it.