When Tally is wearing the pig fancy dress mask, the folded ear of the pig mask swaps from the right hand side to left hand side, and then back to right hand side.
When Tally is practicing shooting the crossbow with David, her head wound is fresh again.
When David finds Tally in a forest fire. The smoke would have killed them.they had no breathing apparatus.
When they are pulling up the train tracks and saying they recycle the metal they call it the 'ties'. A railroad tie is not the metal part; it is the large wood block that goes perpendicular to the track that 'ties' the track together.
While in the world of Pretties a symmetrical face is valued above all, in the movie both Dr Cable and Peris (the Pretty main antagonists) do not have symmetric faces.