Continuity mistake: When he's saying goodbye to Joe, David's hair is alternately dry/wet and swaps styles between shots.
Continuity mistake: Before David gets stabbed in the pool, the hair of the guy with knife is messy, but during the stabbing it's brushed.
Visible crew/equipment: When David drinks from the empty glass, two huge lighting screens get reflected.
Continuity mistake: When David talks to the Fair, from the angle behind, he is standing parallel to her, from the front angle he is standing sideways.
Continuity mistake: After Prof. Hobby leaves his glasses on the desk to stab a student's hand, the glasses turn 180ยบ around.
Chosen answer: His license is a tracking device. By removing it, he's preventing the authorities from easily tracking him.