Black Castle - Door bugs on last boss



In the Black Castle dungeon, if the group wipes at last boss, the door is bugged and doesn’t open anymore. It happened to me yesterday on Crom, and also some time ago to some friends of mine on Saga.
Can you please fix it? It’s not easy to find a purist group for these dungeons, and it’s very frustrating to reach the last boss and could not complete the instance because of a bug.