I have in the past had problems with sudden deceleration caused by my accidentally brushing the RH scroll wheel determining TACC target speed. That was disconcerting enough but at least there was an obvious reason for it. Last night however towards the end of a 300 mile drive, much of it in pouring rain, my Tesla decided to change the target speed all on its own. I was driving at 65 just coming off the M25 on to the M3 eastwards when the speed suddenly shifted down to 45 mph. I then scrolled it up to 55 because I was slowing down anyway - but then just as I was about to merge onto the M3 it suddenly jumped to 65 mph which was too fast for current road conditions. This was one of the trickiest moments I experienced in my long 600 mile round trip, which included several panic-braking incidents caused I think by gantries over the road (reminds me of the Young Ones sketch where the aircraft pilot suddenly screams in terror, “Oh no — a cloud!”). Quite apart from the dangers it creates of following cars rear-ending me, it is just so embarrassing when you have passengers..!