It may not work every time but it has worked, twice for me alone and for a number of other players as well. Both of mine were quests to "Own x building" so I couldn't try the other possible workaround you might have with your quest to "Own x resources" (empty your Storehouses of all the required resource then get it back, also mentioned in the first post.)
Regarding "Produce at least 500 Musk Deer Fragrance":
Any chance you happened to make exactly 500? Just to make sure it's not just the wording that's off.