Continuity mistake: In the beginning, Serena approaches the man to buy the puzzlebox. He pulls the cigarette out of his mouth and exhales smoke, which mostly dissipates. The scene then cuts to the opposite angle, and suddenly, more smoke appears in the air between edits.
Continuity mistake: When Riley and Trevor are "play fighting" in Trevor's apartment at the beginning of the film (right before Trevor explains his plan to rob the storage unit), a cigarette suddenly appears in Trevor's hand between cuts. (His hand was empty in the previous two shots and he had made motions indicating he had put the cigarette down on the table before that).
Continuity mistake: When Riley and Trevor are talking in Trevor's apartment at the beginning of the movie, Riley lights up a cigarette that they share. It can be hard to notice, but the amount of cigarette that is burned up and the amount of smoke in the air subtly changes instantly between shots a few times over the 30-or-so seconds the cigarette is on screen. (Since the scene would be shot over multiple takes and angles, it'd be impossible for it to 100% match every time).
Continuity mistake: When Joey is talking to Voight about the puzzle box and Voight tells him to "Keep going," pay attention. It's kind of hard to notice, but if you look closely, in the over-the-shoulder shot facing Joey, you can tell that Voight is standing straight, facing Joey before it cuts. When it cuts to the opposite angle, suddenly Voight's body has rotated about 90° (to his right).