Continuity: The Union Flag colors being carried by the lancers as they are about to go into "the valley of death" is flying upside down. In all the subsequent shots the flag is the correct way up.
Revealing mistakes: After the massacre, Flynn sympathetically listens to Major Singh crying over the body of his murdered son Prema who is clearly wiggling his toes in the foreground of the scene.
Anachronisms: In the first ambush scene, some individuals on both sides were armed with single shot Sharps Carbines, which were American made and didn't exist at that time.
Continuity: When the troop first arrives at Chukoti, the British (Union) flag is flying upside down - long before the fort was in distress.
Continuity: When Vickers jumps off the ledge onto an attacker, the ground changes from sunny to shaded between shots.
Continuity: The way Perry's hand is on his sword changes, when he is told he is going to Lahara.
Revealing mistakes: When Randall is preparing to go over the wall to Lahara, a lighting effect is used to suggest clouds passing in front of the moon, so the amount of light varies. However, the effect is interrupted as Randall puts on his hat.
Plot holes: A single shot kills Randall. How is it that this was not heard by anyone, or reported to Vickers or the Colonel?