Continuity mistake: Periodically, we see beyond the wall, where it appears to be heavily forested just beyond the wall and a distance beyond. However, once past the wall, the group starts with a cliff down and then it is completely barren, with completely different weather conditions (frequent red rain).
Continuity mistake: When Four tells Tris that he found out that he's damaged he is sitting at a table eating. On the table there are two small bowls that look empty throughout the scene, however, when Tris gets up to leave and pulls her hand away from Four's, in the close up shot one bowl is now filled with food, and both bowls are in different positions on the table.
Continuity mistake: Many times in the movie, Romit's hair changes from one shot to another. It goes from very short on the sides to long then back again. (00:59:30 - 01:11:20)
Continuity mistake: When Four manages to get upstairs, he tries to tell Tris of the bureau's true intentions and that she is being lied to. But she rejects his ideas and joins David in the elevator. You then see Four being escorted away toward the door. But as Tris and David's elevator begins to go up, you see them looking down at Four, who is looking up at them, from the same spot he was in when he was pleading with Tris.