I think this is just an other instance of the "not updating properly upon an event" curse of the whole development...
If I lose control of a town or an outpost due to ennemy/monster destroying/taking control, then the overlapping ZoC is not properly processed and some random/inconsistent ZoC is displayed. As usual, reloading the game correct this behavior...
Exemple: Town lost due to rampaging Dragon:
Reload of the same game at same turn:
