I'm not sure if it is as designed or a bug...

But please have the shackle key marked as stolen to prevent sale to NPC merchants, or strip it on quest completion.

Ref: Girl by the stairs to the gate - can't remember the NPCs name. Apologies.

That would be Josephine.

But do you refer to the quest, or actual shackles in-game that PC's can use? I am guessing the former, but just to get facts straight.

The shackle key to open Josephine's manacles, specifically.

Adding this to my to-do list tonight.

Fixed.