I have found that it's possible to have a unit stack appear in the wrong region after you have manipulated it in the unit info box at the bottom. The exact methodology is unclear, but this is what I think I did:
1) Select a region where there are more than one force.
2) Select one of the forces.
3) Move the map a bit by scrolling.
4) Drag the force's tab to another tab. Here's where it's weird: it seems that it's possible to either "miss" the other tab and the unit ends up on the map where you dropped it, which could be another region. It might also be when the two stacks can't be combined.
The result is the unit appears on the map in the wrong location, but is still actually located in the proper spot. In the above example, if the unit I was selecting was in Montgomery, PA, and through my fiddling with it appeared to be in Alexandria, VA, if I deselected the unit than clicked on it's counter in Alexandria, it would still say "Montgomery, PA" as its' location. It would not say "en route to Alexandria".
HOpe this is clear. I'll try to repeat it more consistently. It's happened to me a few times, so I suspect others have seen it.