What Austin said. You have to remember, Ryan made the quest tool so it doesn't have absolutely everything for a quest to be done completely and 100%. Such as:
NPCs spawning when a player does an action
NPCs attacking you
New quest step when an NPC dies
Preventing a quest step from being completed more than once
Something permanently changing after a quest step
Scrolls, books, puzzles, etc having the correct text and working properly
Entering a place triggering a quest step
Object interaction
Object dialogue
NPCs disappearing after a quest step
NPCs turning into a different NPC
Quest journals text crossing out in different order
New areas
NPCs that are involved in more than one quest not interrupting
And bugs that are preventing some quests from completing >.<
Other things that I can't think of right now :l