Other mistake: When Deckard visits the Tyrell Corporation, he prepares to test Rachel with the "VK" machine. He is shown putting his briefcase of the table and lifting the "VK" machine out and onto the table. If you look closely, the "VK" machine is already on the table and Harrison Ford is miming the lifting - there is nothing in his hands!
Audio problem: Deckard (Harrison Ford) investigates the maker of artificial reptiles; an Abdul somebody. It's obvious that the dialogue was added as neither actor is in sync with the sound. The end of the scene has the storekeepers voice telling Deckard the information he was seeking while Deckard's mouth is the one moving. Deckard's mouth continues to move even after Abdul's lines are finished and the scene cuts. This has been corrected in the 2007 Final Cut of the film, but exists in all previous versions.
Continuity mistake: When Decker shoots the snake-woman replicant, she hits the glass and in one shot you can clearly see that is not the actress that hits the glass, but a stuntperson dressed like her. This has been corrected in the 2007 Final Cut of the film, but exists in all previous versions.
Revealing mistake: When Zhora dresses in Taffy Lewis' club she puts on high-heels. Later during the chase scene and when she flies through the windows, she is wearing normal boots. And when she is shot the second time, her right hand holds a control, probably for the blood bags on her back.
Continuity mistake: When Deckard shoots the snake-woman in the back and she falls through several layers of glass she lands on her stomach, with her head lying on the left side. In the next scene Deckard is standing beside her, but now she has turned her head, lying on the other cheek. Her arms also change position.
Audio problem: In one of the scenes at J.F.'s house, J.F. is talking to Batty and Pris. Batty is sitting down and starts talking about J.F.'s chess game. Batty says "your opponent" then J.F. says "Oh, Dr Tyrell." While he says this the chess game is shown, then it cuts to Batty and J. F. and he continues "I've only beaten him once at chess." For this line his lips are not moving.
Revealing mistake: When Deckard has the dream of a unicorn, it races towards the camera and you can see its horn. The horn is wobbly, revealing it's just stuck to a regular horse. [Note: this has been cleaned up for the Final Cut release, but can still be seen in earlier versions of the film.]
Continuity mistake: After Pris and J.F. Sebastian startle each other, they begin to talk for a moment. Watch J.F.'s hands as he says "Don't worry, I won't hurt ya." In the side angle, his left hand is hidden and his right hand is fidgeting with the bag he is holding at his chest. It then cuts to a view from over Pris' shoulder and suddenly his right hand is now hidden from view and it's his left hand fidgeting.
Continuity mistake: After Leon puts his hand in the freezing liquid holding the eyes, warranting several angered scolds from Chew, Chew looks at Roy in puzzlement. Between this shot and the shot after Roy says "Yes... Questions." The head gear on Chew's head moves up on his hat. The position of it changes several times during this scene.
Continuity mistake: After Gaf takes Deckard to his police car to go see Captain Bryant, he looks at a screen that is blue, then turns red and says PURGE. He looks down and to his right when he sees this. Moments later as they are flying in the vehicle, a view from the back seat shows the front dash with two screens. The one in the center, which would have been the one he was looking at since he was looking down to the right, is now much skinnier than it was moments before. It's the one showing green and orange text now.
Continuity mistake: After he finds dead Pris, the blood smears on Roy Batty's lips change. He touches her bloody wound with the fingertips of his right hand and then presses them to his upper lip. You will see two parallel smears of blood. Moments later there is only one smear going from his upper lip all the way to his chin.