15:03: Maddie writes a joke ending to her book.
18:47: Ending shows on screen again, this time with an extra blank line between "THE END" and "money now please."
When Maddie Drops the bolt outside on her porch and Man picks it up to break it, its clear the bolt is made from wood, whereas in fact, crossbow bolts are usually made from carbon or aluminium.
When Maddie takes shelter in her bedroom, she closes the door and pushes a dresser in front of the door with great difficulty. After the killer uses Sarah's hand to bang on the window and Maddie backs out of the room, she pushes the dresser out of the way with one hand and little trouble.
When Maddie is typing on her Macbook she is using Messages to speak with her neighbour. When the power runs out and she switches to her phone she continues the chat in progress however her iMessage function is not turned on. None of the previous messages from her Mac should have been shown.
There is a visual glitch on the first photo the killer sends to Maddie.