Now let's think about this one. The cop is seen with his jacket on in one scene, and then in the next scene, it's off. This might just be me, but i have discovered that even cops have the ability to take their jacket off.
I believe this is an adequate slip-up. I know that the police man could have taken his jacket off when the cammera cut away to show Ferris on the float at the parade, but I believe in this particular scene the cop is supposed to be chasing Sloane and Cameron and would not have time to evacuate his jacket and place it neatly out of cameras view. I do not believe this was the intent of the scene, but it is a monor slip-up and would not be noticable unless pointed out.