Continuity mistake: At the start of the movie, Christoph Waltz shoots the horse in the head, but later the bullet hole is seen in the horse's neck.
Revealing mistake: When Django kills big John Brittle, right when he smashes his face on the floor, a cushion pops-up. Most probably hidden among the leaves to soften the fall.
Continuity mistake: When the maids introduce Brunhilda to Schultz, she is either looking at him or sideways, depending on the angle.
Revealing mistake: Before confronting Stephen, Django shoots Candie's sister. He is up high on the stairs with her on the first floor. He is far to her right. But when he shoots her, she flies straight backwards into the other room, and you can see where her dress was pulled by a rip line.
Factual error: In several closeups (especially of Leonardo DiCaprio) it is clear that some of the characters are wearing plastic contact lenses in their eyes. These were not invented until the late 1970s.
Continuity mistake: When Django shoots the snowman, the damage to it appears/disappears/increases/decreases between shots.
Factual error: When Big Daddy is on the front porch talking to Bettina there is a security camera above and to his right on the porch overhang.
Visible crew/equipment: When Sheriff Bill Sharp steps out into the street you can see a hearing aid in his left ear.
Continuity mistake: During the skull monologue, Schultz's hair swaps from messy to brushed between shots.
Continuity mistake: When Schulz and Django ride up to the first plantation they visit, the number of slaves milling about in the background varies with each shot.
Continuity mistake: When Stephen brings Broomhilde to Candie to discuss her price, Stephen is grabbing the left side of her neck in the wide shots, and the right side in the close-ups. This changes back and forth.
Continuity mistake: When one of the Speck Bros. lays injured on the floor, the lamp on the floor is laying right net to the hat, or several centimeters away, depending on the angle.
Continuity mistake: When Schultz and Django first camp, Schultz is seen putting on pants and suspenders. In the next shot he doesn't have the suspenders on, but we see him hiking them up as if for the first time.
Factual error: There are no Live Oaks growing in Tennessee. They can be seen in several outdoors scenes.
Other mistake: When Calvin sits down to eat his white cake, the cake is a new slice. When the camera switches and comes back, it is almost gone. When the scene switches again, he is eating a full piece of cake again.
Continuity mistake: When Dr. Schultz shoots Candie, in the 'reaction' shot where it zooms in on Stephen screaming, Candie's bodyguard (the one with the mustache and bowler hat) has already turned around to see what just happened. In the very next shot he now has his back to the camera and then, a second later, we see him slowly turn around again to see what just happened.
Continuity mistake: After Calvin cuts his hand and forces Broomhilda to sit down, Stephen places his hand around her neck. A shot later it’s on her back.
Continuity mistake: In the final scene where Django asks Cora to say goodbye to Miss Lara, he holds his arm with the gun outstretched, but in the next frontal shot he keeps it lowered.
Continuity mistake: After Calvin yells "where is my beautiful sister" the sun changes between shots.
Continuity mistake: Towards the end while Django is taking the horse from the cart with the slave cage, the sun changes between shots.
Answer: Django and Schultz killed some of Big Daddy's farmhands, and he wasn't going to let a freed slave kill some of his workers. Schultz knew Big Daddy would come after them for what they did. Plus Django would never let go of a chance to kill a slave owner who was trying to kill him.