Revealing mistakes: When the bed sheet is being pulled up over Betsy, right when the lightning flashes, a string or wire is clearly visible.
Miscellaneous: In a night scene where the light from the candles and fireplace are systematically blown out, James Johnston immediately picks up his Bible and begins reading in the dark.
Anachronisms: In one scene the sky is shown with clouds, and an obvious jet stream or contrail streak to the left.
Crew or equipment visible: Right after John Bell gets knocked out by the door slamming shut, the "spirit" re-opens the door. A hand can be seen quickly pulling away from the knob on the other side.