During the dance scene at the beginning, the camera pans all around the room, but not one musician is to be seen.
In some scenes you can see mountains at a distance. However there are no mountains in the central part of Russia.
The episode is set in 1805, but shows the General Staff Building in Saint Petersburg, which was built from 1819 to 1829.
The Vicomte de Mortemart, in Russia after being displaced by the Revolution, is seen wearing the insignia of the Legion of Honour, which was introduced by Napoleon. No supporter of the French monarchy would have worn any such award.