Continuity mistake: When Alex and George are stuck in the elevator with the doors slightly open, with the gunshot wound victim, there is blue paper lining the slight opening in the elevator doors. However this paper disappears in some shots, the reappears again. (00:18:40)
Character mistake: Ms. Bitzer says she's booked a trip to Iceland to experience the sun never setting. While the sun does set quite late there, Iceland is located south of the polar circle and does not have midnight sun. And either way, season four has been established as taking place after summer, so there wouldn't be midnight sun anywhere.