Nostalrius Begins - Quality wow vanilla realm (1.12)

I'm not able to collect the crystals for the quest "Draenethyst Crystals" in the Swamp of Sorrows. When I try to pick up the Crystals, it only says "That is already being used" and doesn't even show a loot frame. Has anyone made other experiences with that?

This quest is bugged for me too. Same problem.