The background for the opening titles is a map of the Panama Canal. The orientation of the map and the compass is correct, but the labeling of the map is incorrect. In fact, the Atlantic end of the canal and the city of Colon are at the upper left (Northwest), and the Pacific end of the canal and Panama City are at the lower right (Southeast). The map is correctly labeled behind the closing credits.
It is true that Officers can be "Dismissed" but only enlisted men are "Dishonorably Discharged." This is true and Captain Leyland (Bogart) says conversationally that he was "...dishonorably dismissed," and never uses the other, defined term: "Dishonorably Discharged." There doesn't seem to be any factual error.
In an early scene, we see a court martial proceeding and afterwards Army Captain Rick Leland says he has been dishonorably discharged. In the US military, that status can only be applied to enlisted men. Commissioned officers convicted in a court martial may be dismissed, but they are not dishonorably discharged.
As Leland (Borgat) is entering through the glass door to the NYK Line Agent's Office (to buy a steamer ticket) there is a nearly square flag painted on the door. The flag shown is a red circle with TEN rays extending from it to the edges in a sunburst pattern. It NEVER existed! The appropriate ensign/flag for a non-military maritime organization such as Steamship Company in the immediate pre-war period would have been the meatball* on a field of white - or, the same as the nation's present flag. The nearest thing to what is shown is actually one with only eight rays flown by the "Japanese Ground Defense Force." It was the sunburst flag with sixteen rays that was widely - even universally, used by the Japanese military (Army & Navy) throughout WWII - generally up to 1945. ((*) The red circle used by the Japanese for both flags & aircraft roundels during this period was in those days uniformly referred to by all of the Allies (military & civilian alike) as "The Meatball.")