When you go to loot the container (the Blood of Heroes item on the ground) a loot box does not come up and the container does not spawn a Fallen Hero NPC once looted.
Because all the containers share spawn timers, when all the Eastern Plaguelands containers have been looted, they eventually all spawn in Western Plaguelands spawn points where they just bug out. Because they can’t be looted, the Blood of Heroes container doesn’t despawn and thus locks everyone out from ever being able to loot any Blood of Heroes container.
Edit: This is for WoW Classic.