[PC] Map of Watcher's Pass treasure bugged

I finally got back to the game after not playing for most of a year and I find I can't complete the Map of Watcher's Pass quest. I've found the spot, I have the map and the quest is in my quest journal, but there's no "there's something in the area to look for" indicator, and when I search there's nothing there.

I've even checked a video walkthrough online and I'm in exactly the right spot. There's a small patch of white dirt but nothing happens when I search.

Has anyone else encountered this problem, and is there a fix? Exiting and restarting the game did not help at all.