Character mistake: Watson says that there are fifteen windows on the front of 221B Baker Street, but if you look, there are only twelve.
Character mistake: At the football players funeral, the guy on the left is still breathing, despite being dead.
Character mistake: When Dr. Walker and Michelle are dancing at the club, the people around can't help but stare at the camera.
Character mistake: On the way to Jerusalem, Poirot says that "that man, Weizmann, put it rather well the other day, before Lord Peel's commission", and gives a famous quote about the world being divided in 'two places' for the Jews (those where they are not allowed to live, and those they cannot enter). The movie takes place in May 1937, and Chaim Weizmann's quote is from November of the previous year. 6 months are hardly "the other day."