Continuity mistake: The piece of paper that had "MIN" written on it suddenly changed from being in the corner of the table to being on the left side of the planchette (heart-shaped pointer), which was near the center of the Ouija board and table. (00:10:20)
Continuity mistake: The straws in the three glasses in front of Abby are at different angles several times. (00:10:55)
Deliberate mistake: In the dark, dilapidated house, Margaret asked Abby, "What's that?" and Abby was able to illuminate a large portion of the room with a disposable lighter. (00:16:35)