Poppy's By the Tree (1) - S2-E1
Factual error: At the end of the episode, the killer shoves a long machete up through the mattress. This isn't possible considering he's under a bed and there's not enough vertical space to shove a machete straight up.
Poppy's By the Tree (1) - S2-E1
Revealing mistake: When Al, Peg, and the kids get to their room, notice the "hole" in the blanket on the bed. It's there the entire episode so at the end, the killer can shove the machete up through it.
Poppy's By the Tree (1) - S2-E1
Continuity mistake: Bud asks to go down to the high school "tomorrow" to meet the man who met Andy Griffith. Earlier Al reads the events page in newspaper. The event was said to be "tonight."
Poppy's By the Tree (1) - S2-E1
Continuity mistake: When Kelly walks over to the table, she burps. She breaks character by laughing with her head down yet a second later, she has a serious look on her face.
Answer: It was one of the hoses connected to the engine, nothing specific, but to indicate that Al tampered with the vehicle.