Audio problem: In 6.14 "Mannequins 3: The Reckoning", when Dean goes up to talk to Ben, Ben is playing a video game. Dean says something along the lines of "There's no way plants could kill zombies", therefore pointing out that Ben is playing Plants vs. Zombies, but the sounds coming from Ben's gaming system are not from Plants vs. Zombies.
Audio problem: Dean is in the cemetery talking to his father's grave, trying to figure out what's happening to him. In a continuous shot, right after Dean says "like it doesn't want me to be happy", you hear him say, "of course I know what you'd say" but his mouth doesn't move at all. (00:23:00)