I didn’t have any issue with this quest with my main char, but I did face a buggy quest in another one.
This is my alt… which I’m going to take my time to level whenever I’m free.
Bahhh.. I seriously need to farm for money instead of leveling my alt.
Anyway, if you’re facing difficulties in retrieving the Captured NuKaruka, just abandon your quest and re-take it.
In fact, if you face ANY buggy quest, abandon them and take the quest again from the NPC.
I was so unlucky that I had to retake the quest 3 times on my alt!
By the way, for this particular one, you don’t need that mallet thingy.
It’s supposed to just drop after it dies.