Audio problem: When Jodie Foster first hears a ring at the front door, Steven says, "The police." and Jodie says, "You called the police?" He responds with, "Of course I did. You scared the s*** out of me." When he says, "You scared the s*** out of me.", his mouth movement does not match what we hear.
Other mistake: Near the end of the movie Dwight Yoakam is holding Jodie Foster's daughter captive as he tries to exit the house. Jodie Foster sneaks up behind him with a sledgehammer and swings it at his head. He turns to face her and the metal end of the hammer catches him firmly in his temple, knocking him down a flight of stairs. A few minutes later he comes up the stairs and tackles Jodie Foster to the ground, seemingly unhurt by the impact of the sledgehammer.
Trivia: The shot of Meg turning on the security screens took 57 takes before director David Fincher was happy.
Question: I don't really understand why Jodie Foster's character didn't tell the police something was wrong when they came to the door. I know she was worried for her daughter but the robbers couldn't overhear and she could have asked the police to come back later, giving her a chance to smash the cameras. Also, considering that she emphatically denied there was anything wrong, why did the police return later with all the guns etc?