Glitched Priorite Shard - Southern Reach Gate

I've completed the full game and I'm only missing one priorite shard (99/100). The only treasure icon on the map is at this location. However, the skull is untargetable, and I don't see the priorite in the skull's mouth. I've tried different angles, saving and reloading, going to other locations and returning. Nothing has fixed it. Please help, this is standing in the way of me finishing all achievements in the game.