Bugged quest: Chen's Empty Keg

In the Barrens I picked up Chen’s Empty Keg in the barrens and handed the quest in to Brewmaster Drohn in the Barrens. I received a follow up quest also called Chen’s Empty Keg, which required me to collect a variety of items around the barrens. On taking all the items to Brewmaster Drohn the complete icon was greyed out and couldn’t be completed.