Deliberate mistake: The ghost opens Nikolaj's bedroom door an inch or so, yet there is enough light emitting onto the hallway floor for the door to be open about halfway. After the door closes, the light on the floor continues to gradually fade towards the closed door. (00:17:05)
Deliberate mistake: When Flash is at the coffee store, the pavement is dry. When he exits the place dressed as The Flash, it's wet for cinematic purposes, but a mistake nonetheless.