Revealing mistake: In the scene where Norman visits Caleb at the motel on his own, after hearing Norma and Dylan argue, he gets into an argument with Caleb. Norman then pulls a knife out high above his head, at which point you see it is a prop/rubber type knife. The handle aimed at Caleb but the force Freddie Highmore has used to pull the knife up and back causes the blade to bend and aim toward the ceiling.
Other mistake: After the scene where Norman texts Bradley that he is coming over, the next shot is Norman looking at the small transcript of his messages to her. If you look, you can see that the transcript starts at 2:34 PM. However, it's nighttime. You can even see the time says 2:34 PM at the top of the phone screen. Also, the original text of 'Hey' is missing although he texted her immediately after receiving it with 'I want to come over and see you.' (00:37:40)
Revealing mistake: At the beginning of the episode when Emma is talking with Norman, she drops the newspaper (of Bradley) in front of him. If you pause it and read the newspaper you can see the text has been repeated once for the text about Bradley and many more times for the news item below that. (00:41:35)jayixz