Continuity mistake: When looking at the dog from the bedroom window, there are 2 windows in the room facing the dog. When we see the window from outside only 1 window is lit up, despite both being in the same room. (00:11:30)
Continuity mistake: When April and Carolyn are playing Hide and Clap, the blindfold on Carolyn keeps moving. Note the amount of skin visible above the blindfold and under the hairline. (00:25:30)
Continuity mistake: After being chased in her house, Judy closes the door to the bedroom and proceeds to put her hands on her ears, underneath her hair. The very next shot, she still has her hands on her ears, but it is over her hair.
Continuity mistake: When Lorraine sees Rory in the music box mirror, the items on the wall should be reversed, since it's a mirror, but they are not. When she turns around to look, everything is in the exact same position.
Continuity mistake: When Rory throws the teddy onto the table its position changes when he runs outside to see why Cindy is screaming. (00:15:00)
Continuity mistake: When Rory sees the porch door open by itself it is wide open. When he approaches the door, it is only ajar. (00:21:15)
Answer: It is explained in The Conjuring 2 that Lorraine has a premonition of Ed being impaled.