Nostalrius Begins - Quality wow vanilla realm (1.12)

The quest called "The Lich's Identity" is impossible to finish. You can start this quest by taking it from Bethor Iceshard in Magic Quarter, in Undercity. If you want to complete it you have to go to the island in Brightwalker Lake and acquire the Lich's Spellbook. Unfortunately, you can't pick up this book. You get a message which states that this item is already being used by someone else even if no one is around you. Can you please fix that?
Thank you for reading.

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