The Red Door - S2-E9
Continuity mistake: When Big Jim communicates to the military commander at the dome, he writes on his notepad, and shows "Me and my son" to the commander; yet when he returns to his car and looks at it again, it's written quite differently. (00:24:05 - 00:24:45)
Other mistake: When Norman and Madeleine are talking outside the Motel about Sam, the left side of the screen appears to be split down the middle after Norman says "Because you know it's safe to tell me", causing a weird effect on the chair that Madeleine is sitting in.