On more than one occasion, when driving in enhanced auto-pilot and engaged auto lane change, the car started changing lanes, then abruptly swerved back into my original lane. i looked behind me and coast was clear. it's not at all apparent why the car aborts the lane change. i was driving the speed limit, 65 mph on a 3 lane highway and i was in a middle lane, changing into the right lane. first occurance was in traffic with plenty of space between vehicles to execute a safe lane change. once the vehicle returns to the original lane it will attempt and successfully change lanes. other occurances similiar in nature. when rounding a curve and executing a lane change with ehanced auto pilot on, the manuever is more abrupt, serious safety concern. all engaged functions of auto pilot disengaged due to erratic movement. as mentioned, this is an ongoing problem and on other tesla blogs similiar occurances are reported. a bulletin needs to be issued relating the problem and hazard to tesla owners and tesla needs to supply a fix to the problem