Other mistake: When Farley Granger sneaks out of his flat to go to Robert Walker's house, there is an EXIT sign over the door. Maybe in a theater or cinema, but in a private apartment?
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Suggested correction: 1) This only appears in the preview version of the film, not the final version. 2) Why would an apartment building not have an exit sign? Can you cite a reference for this? I would think someone making a contemporary film would notice if it was such an obvious error you think it is.