As for your lane change working & not working, can you elaborate on this? Is this on the same stretch of road or different roads?
Auto lane change only works on limited access highways (at least that's my experience). Even though you may be on a road with a median and multiple lanes, but one that at grade intersections, auto lane change will not be available.
So if you are on a limited access highway (with on/off ramps), the limitation is that the car has to be able to "see" the adjacent lanes. This will be evident to you by seeing gray lane markings showing the lane to the left (or right) of your current lane. When those are present, auto lane change is possible. If it's not showing them, it won't be. Maybe the lane markings aren't visible, or you haven't given the car enough time to "see" them (my experience is that it takes a little while after you've entered the highway for the lanes to be recognized for example).