When Clive first visits his Aunt's house, and the camera pans to the wall, where the animal heads will appear. You can clearly see a lighter patch of wallpaper where one of the heads will later be superimposed.
When in 1919 Candy receives the letter telling him that the whereabouts of prisoner-of-war Schuldorff there's a shot of the letter saying that camp is called 'Hardleigh'. However in voice-over Candy says 'Hardwick'.
Candy's scar is clearly visible on his upper lip when he is in his room at the convalescent hospital, but is obscured by his newly grown mustache moments later when he goes to congratulate Kretschmar-Schuldorff.
Clive Candy goes to confront Kaunitz in Berlin, which is in Prussia, but Kaunitz's Stammtisch are drinking from Hofbräuhaus krugs, noted by the 'HB' insignia. The Hofbräuhaus is in Munich, which is the capital of Bavaria, 360 miles away.
The notice Candy places in The Times about Murdoch's death states he died in a bombing raid in October, 1940. But when Candy is shown on the cover of Picture Post magazine sometime afterward, the magazine is dated September 21, 1940.