I do not have the $4000 AutoPilot feature installed. I do have AutoDrive which has two modes--manual steering and auto-steering. I have tried to use the first mode (MS) on many occasions and have noticed some pretty disturbing issues. I'm wondering if it's just my Model X or a more pervasive issue. When I was driving yesterday in local traffic, there were several school zones and a heavily enforced speed limit coming down 165th in Redmond. I used the MS mode to keep me locked on the car in front and at 30 mph. When the car ahead switched lanes, I stayed in my lane and my Model X got confused and slowed down unexpectedly. I had to take over and accelerate through the intersection before being rear-ended by the car behind me. This is not the first time this has happened. I've had several cases where on MS that the vehicle slows down unexpectedly when the cars ahead move out of the way when I expected my vehicle to continue at the same speed or accelerate to the set speed. On a related note, my daughter was following me on MS the other day and notice that my brake lights were not coming on as I slowed. Is that a common occurrence? On AutoDrive (AS) (auto-steer): I drove to the airport last night in very heavy traffic at a very low speed. AS kicked in on request, but even with my hands on the wheel it would drop out. It seems that when I engage AS, the car turns a bit in either direction almost as if it's testing if my hands are there. If I provide too much resistance, it kicks out. If I concentrate on not holding on too tight, it seems to work better but soon kicks out again. Is there a tip or setting I should check?