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.
Other mistake: According to the cops at the door, Meg's husband revealed to them that Meg said "There are three" on the phone before the line was cut off. However, earlier in the film during the call, Meg said "There are three men..." and then the line was cut by Burnham. The husband would have heard the word "men" as well to give to the cops.