When Ethan is drawing a robot head on the board, the close-up shot shows him drawing an X in one of the eyes but in the other shots there is no X.
In the last scene, when Justin is unlocking the door to Rebecca's house his hand goes to the bolt as if he's inserting the key. You then hear the sound of the bolt unlocking but from the perspective the audience has of the inside of the house the lock never moves and is also in the unlocked position the entire time.