Continuity: The lights on the Seine tour boat go out, but in the long shot they are still working.
Boom mic visible: As Reggie and Sylvie are walking around the indoor swimming pool, the boom mike and boom arm are reflected in the glass as they turn the corner.
Continuity: After Peter Joshua is sprayed with a water gun by Jean-Louis, the water patterns on his jacket vary between shots.
Miscellaneous: The sign outside the embassy would not read "American Embassy" it would read "Embassy of the United States of America" or "Ambassade des États-Unis d'Amérique".
Revealing mistakes: When the morgue technician closes Mr. Lampert's drawer, the shot from inside the drawer shows the attendant's hands on the inside, too.
Factual errors: Gluing valuable stamps onto an envelope greatly decreases their value.
Continuity: When Alex and Reggie are on the restaurant boat, a man appears and disappears behind them between shots.
Factual errors: Scobie is covering "Dyle" with a gun held in his artificial hand, so there's no way that he can pull the trigger.
Audio/visual unsynchronized: When Mr. Bartholomew uncorks the wine bottle in his office at the embassy, an uncorking sound is heard, but no cork comes out on the corkscrew.
Errors in geography: Regina, fleeing Canfield, rides the Metro from Saint Jacques (signs prominently seen) to Palais Royal (mentioned several times in dialog). From Saint Jacques one cannot get anywhere near Palais Royal without changing trains at least once; but of course she never does (because Canfield would have another chance to catch her).