When Lord Streetly, an admiral, is talking in the opening scene, he says the fleet will arrive at "23 o'clock". As a military man he would undoubtedly say 2300 hours or,at a pinch, 11 o'clock in the evening but not 23 o'clock.
When Fabian first suspects that Danforth is not what he seems, he uses a pen to scribble a beard on a photo of British Intelligence Agent Richard Burke in his notebook dossier. The beard he draws ends in a straight line under Burke's chin. In a later scene, when Fabian shows the photo to Norvel, the beard is thicker and descends with a point toward Burke's collar.
While George Sanders tries to employ a French accent, his interaction with the accents of [Link:nm0793574] (Japanese) and [Link:nm0000048] (German-inflected English while affecting a terrible Japanese accent) clearly causes him problems.
As this film was among a number released the same year in the rapid "film factory" pace of the studio, several title cards were prepared early, assuming they would be released the same year as the copyright on the cards. While the film was made in 1938 and carries a 1938 copyright, it was not released until 1939. Meanwhile, the newsreel scene shows the Movietone News as having a copyright of 1937.
The sign for the Sultana Theatre appears to advertise the film Charlie Chan in Honolulu, but it clearly reads "Starring Warner Oland", and that film featured Sidney Toler, not Oland, as Charlie Chan. However, this is very likely not an error but done in tribute to the recently deceased Mr. Oland, a longtime Fox contract star.