Although i've found all caves, and they all show up on the Orb Vallis map, i did not receive the Achievement. The tracker on my profile only shows 29/30, but ive counted them and even revisited every single one of them and they are definitely 30.
Had this problem since November, 29/30 bugged even though I visited all 30 caves and had them appear in the map. Triple checked all 30 caves again and nothing.
Well, today I finally completed Vallis Spelunker by following some hints from other threads. Here is how I did it:
First, you MUST NOT be the one hosting (so no Solo). Edit: If someone else is hosting make sure they load into Orb Vallis first.
Join someone hosting Orb Vallis, make sure that person haven't found any cave or