2017 75D, early May build. Ever since delivery, cruise control (and autopilot) fail to work intermittently, about 1/2 the time overall. When it works, it works from the time the car is started for the entire trip. Other times, from the start of the trip there are no visible lane marking on the dash pictogram, and I get "Cruise not available" when the stalk is pulled. Autopilot won't work either, of course. When it's not available, it's not available for the entire trip. Turning the car off and on doesn't help, resetting the main screen doesn't help. When we start our next trip it's anyone's guess: cruise may work or it may not work. Doesn't' matter if car and windscreen are clean. We spent some time on the phone with Tesla support and they verified the problem. Told us there might be a hardware problem, but we scheduled a service appointment last week and they determined it was a firmware problem. They updated us to 17.24.28. Got car back; problem unchanged. I checked back with them and they said this was a known firmware issue and a future update (timeline unknown) would fix the problem. In the meantime, I drove two hours on the highway yesterday with no cruise control (first world problems, I know), and am getting a little impatient with it will be fixed "sometime". If this is a known firmware problem, it seems like I should be seeing a lot of posts from other recent delivery owners experiencing the same thing. I haven't seen that. About a year ago or more some owners reported getting "cruise unavailable" messages which would usually correct in a few minutes. Seemed to be fixed by re-calibration of the radar unit. Anyone else having this problem?