I just drove from Silicon Valley to Santa Barbara and back on 101 in my 17.17.4 AP2 MS. About 700 miles I used autopilot most of the way and it worked very well. Auto lane change was another matter. About 20% of the time, the car wouldn't change lanes. Speed, lane markings, straightness, and traffic conditions were all ideal for a safe lane change. But Sparky just stayed in its lane, oblivious to the blinking turn signal. Typically, a few miles later, the auto lane change would work. Any idea what's going on?