Other mistake: At the beginning of the movie, we learn that the precogs "do not see what you intend to do, only what you will do" and that they cannot see suicides. At the end, Burgess intends to kill Anderton but does not go through with it; he commits suicide instead. Given these two facts, the precogs should not have seen Burgess' confrontation with Anderton at the end, and a red ball should not have been created.
Continuity mistake: When we see the Leo Crow previsions for the first time, we see the numbers "9" and "6" backwards because we are seeing the previsions from behind the screen. But in the cyberparlor we see the previsions from the same side that Anderton and Riley are watching them, and the numbers are still backward.