When playing with a new player trying to do the Witch side quest (to get the candy cane) the quest will mark as complete for both if only 1 player has all the items. I had everything on me and could speak to the Witch when my buddy was outside but as soon as he came in we could not talk to her. So we had to go gather everything for my buddy too, not really knowing when he had all items since it already showed as complete for him too. But as soon as he had all items we could progress.
