The "A Royal Escort" quest works only until you enter the gate of "The Culling of Stratholme". Here, the NPC we are supposed to protect freezes, it is impossible to talk to him, so the quest in the city is impossible to complete.
But it turns out that due to this non-working quest, the instance cannot be completed at all, because Bosses are not spawned.
Is there any way to count her as Achievements?