Looking for help, Elemental Exercise mission is bugged

My Elemental Exercise mission won't complete after killing the caged zombie, If I type /fixquests I'm given a new book to buy an Elemental weapon with and when I use that to kill the zombie the mission doesn't progress and I am stuck with a copy of the dagger of which I can't get rid of because it is a "quest item", I now have 3 of them.

I'm hoping an admin can delete the duplicated weapons from my inventory since I can't get rid of them and let me finish this part of the quest, please this is just so frustrating.

Edit: I have no clue what happened but for whatever reason the mission let me progress although I just kept doing what I was doing before, however I am still stuck with 3 Study Results books that I hope an admin could delete from my Inventory

 

There's a trick on how to drop undropable item.
First drop an item on the ground, then fill your inventory to the brim alongside with the undropable item.
Then click and hold the item(don't drop it)
Wait till you pickup the dropped item earlier.
Once you picked it up, drop the item you were holding.
I used this technique many yimes and it works everytime

 

You need to give the item the mob drops to the NPC. I assume you randomly killed the mob again and again until you accidentally picked up said item and that let you progress.

 

Thank you, this fixed my problem of excess Quest Items that were for a finished quest

 

you could also throw them into your daily reward or raid reward chest