After Libby (Vivien Leigh) steals six pence from Charles's hat on the sidewalk, she runs to a food stall and orders a coffee. When she orders the coffee and "two doorsteps" her necktie is under the right side of her collar. She then walks around to the other side of the stall on now her necktie is not under the collar.
While ordering coffee and talking to the gentleman whose gold cigarette case she steals, Libby's eyebrows are penciled in thicker. In the next scene where she is dancing alone in the empty house for rent and is confronted by Charles her eyebrows are noticeably thinner.
In the scene where Libby wrecks Charlie's apartment and holds the sewing machine up to throw it, the figure who enters through the door with his back to the camera is clearly a body double for Charles Laughton.