Continuity mistake: At the beginning of the episode, when Del is about to leave the restaurant, the front door has a "Closed for redecoration" sign on it. When the shot changes to the outside, however, the sign is gone.
Continuity mistake: When Del discovers grandad talking to Arthur, he sticks his head through the door. Camera cuts and he sticks his head through again. (00:13:00)
Chosen answer: An apparent long string of illnesses.