Who Are You? - S1-E6
Deliberate mistake: A plumber is looking for a leak under the floor of a house, and sees the bones of a hand sticking out of the concrete wall at the side of the house. The concrete is flat, this is because in construction boards are put up and the concrete is poured in, so how were the fingers sticking out of the boards during construction? In reality, the fingers would be inside the concrete, the workman would see nothing, no plot for CSI.