Revealing mistake: When the first scene at Emma's hideaway was shown, obviously the two characters Emma and Jessica were filmed seperately on the couch and then the film was put together (as both are played by Angela Lansbury). However Jessica did a lot of moving while she was talking, so Emma was looking straight across at where she had been, despite her bending down while she talked.
Audio problem: When singing "Goodbye little yellow bird" Emma blows a kiss to Oliver offstage, but she is still singing the song when she is blowing the kiss. Although it's possible she was pretending as it was part of the act, her voice wasn't even muffled by her hand.
Continuity mistake: When Emma was almost hit by a car she jumped up onto the edge of the wall and then back down onto the floor. When she landed she was facing the theatre door, but when Oliver came of the door and the shot changed, she was facing away from the wall. This happened in the transition from stunt person to Angela.