Load the attached savegame, and try to cast holy vision on the area north-northwest of the circle of power, where the Alterac traitor ships are.
buggy holy vision.sav.gz
I thought it might have been just that map, but no.
buggy holy vision 2.sav.gz
Lots of places on this map throw off Holy Vision, for example near the lower-right edges.
Load the attached savegame, and try to cast holy vision on the area north-northwest of the circle of power, where the Alterac traitor ships are. buggy holy vision.sav.gz
(Wargus 2.4, Stratagus 2.4, Windows 7)