When the Anti-Manchurian League sends a grenade to the Empress, she screams, rolls off the sofa, and briefly her entire leg up her skirt can be seen, clearly in pantyhose. Pantyhose did not exist in 1931; she should have been wearing a garter and stockings.
The Japanese military personnel all speak Chinese with each other, even when they are by themselves inside their own legation. There would be no reason for the Japanese to speak a foreign language inside their own embassy, especially with no other Chinese people around.
The Japanese general wears the insignia of a sergeant, before switching back to general, while at one point his aide (a lieutenant) is seen wearing the uniform of a lieutenant general.