[Bug/Gameplay]Unit doesn't disappear after Sovereign's defeat

These units appear to be leftover garrison units in the enemy cities.  Defeating an enemy sovereign causes the city (and its borders) to disappear, but a unit remains on the location of the main city tile.  The unit is selectable but moving into its square does not initiate combat.

It's not just garrison units, I've seen it with a scout also.

This appears to be similar to a previous report: Enemy unit cannot engage

These guys do seem to go away on a save/load, but since loading seems to be rather unreliable at this point I don't know if its really making them go away or if it's a loading error.