This slip-up occurs near the end of the movie when DeNiro is casing out the the glass house, where he intends to kill the owner. The house is brightly lit from the inside, and is almost completely glass on the outside. As he crosses a large window pane (near the pool) you can clearly see the camera crew running with him. Strangely, it's rather tough to spot if you're not looking for it, but should be rather evident now :P