I don't know if someone else has brought this to the attention of the programmers, if it is I apologize for the repeated topic.
As for the problem... I've noticed that if your are riding a mount and moving into a new area by using your mouse, instead of the directional [or wasd] keys, your character automatically is put on "auto-pilot".
Now, while this this may seem to be nothing more than a minor annoyance when you are roaming about in non-infested enemy areas. It becomes a major hassle when navigating enemy territories, especially when your trying to avoid combat.