I'm not sure it's worth reporting specifics at the moment, as there could be MANY of these kind, but if you have a preferred way to get the data, let us know!
This isn't a bug, per se, it's a case of the quest database data having incorrect coordinates. I suspect this happened when Blizzard rebuilt the old world in Cataclysm, and shifted things around.
In this particular case:
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Cooking Daily for Stormwind
QuestID 26183, The King's Cider, Alliance.
The objective reports the quest completes at coordinates 55.0, 73.1
The actual turn-in, at the NPC Robby Flay, is at coordinates 50.5, 71.9
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I'm wondering, considering the volume of updates, if it would be worth the effort to have a small beta-only module that lets you submit things directly from in-game? While you could do it automatically, the number of people using this addon might make a significant impact on your server, but perhaps when you get a quest, or turn it in, if the coordinates in-game don't match the database, it could ask if you want to submit the correction.
Low priority, but eventually I know you'll want the data itself to be updated... and better for it to be semi-automated than rely on hand-edited submissions I think.