Revealing mistake: In one of Pickett's charge scene the bayonets are obviously rubber.
Revealing mistake: When Michelle is binding Topper's hands to the bed you can see the cloth hiding her breasts. (00:30:30)
Revealing mistake: In the scene where the women are laying in their bunks in the work camp and one lady is describing what she heard about the horrors of other concentration camps, at the end one woman puts up her hands to her face. You can see her fingernails are neatly manicured, something you'd think wouldn't be possible in a forced labor camp.
Revealing mistake: When D'Artagnan is in jail, right after he says "if you give me back my father's sword I'll cut your heart out", when Rochefort hits him in the back of the head you can see the sword handle never touches him. (00:33:15)