Are you holding the directional signal until the lane-change is complete?
If you move the stalk completely, so that it clicks into place and so that you will have to manually move it back into place when the lane-change is complete, then this is unlikely to happen by mistake. But if you simply hold the stalk up or down, and then release it when the car starts to change lanes, it will change back if the lane-change is not nearly completed at the point when you release the stalk. So if you are using the "hold the stalk" method, you need to hold it until the lane-change is very close to being completed.
I realize this may not be the issue at all. Just throwing it out as a possibility.
I've had this happen to me.
This is not my experience. In an effort to minimize "overshoot" on lane changing I let go as soon as I can, which is usually when just
more than half of the car is over the dividing line. I've rarely, if ever, had it "give up" at that point.
No overshoot is possible. You are behaving in a way dictated only by your imagination. Don't do that.
I've had this happen to me.
Sorry can't remember what version. However overshoot was recent (sometime this week). Clicked the turn signal, car changed to the right lane; I was talking with my wife (forgot to de-activate the turn signal), and the car started to drive into the breakdown lane. Had to take over from AutoPilot.