When Rudolf and Hentzlau are face to face, Hentzlau remarks that he left his dagger in Michael. Yet when they are fighting with sabers, Hentzlau draws a dagger from his belt sheath.
The chamberlain, announcing the ball from the staircase as it is about to begin, is seen to change position in alternate shots, from the center of the stairs, to the side, back to the center, etc.
When the conductor conducts the waltz at the ball, his hand movements bear no relation to the music played.
Although it is understandable that the dialogue for the movie would be English, there is no real reason why advertising and other signs in Ruritania should also be in English.
In the opening shot of the movie, showing a train labeled "The Orient Express," there are a couple of very, very tall, California-type palm trees in the background.
When the Count and Rudolph square off, the former offers the latter "a fencing lesson", but they are fighting with sabers which have a technique distinctly different from fencing.