Western Approach Astrarium cave not showing on map.

I've solved all 3 astrariums in the Western approach area. The Western approach tab shows no quests under it, and the "Cave" isnt marked on the map. From the world map, the western approach icon shows "A cave was revealed" when moused over. But when you enter the map there is no sign of that cave being marked. Clearly a bug. Can anyone help at least indicate where the location of the cave is? Thanks.