When Sebastian is talking to Batty about his chess game with Tyrell, the shot is focused on Batty, but Sebastian's chin and lower lip are visible, and you can see that it does not move in sync with the words you can hear him saying.
When Deckard is talking to the snake vendor. You can see through the glass that each characters dialog does not match their mouth movements. This is true in all versions of the film, except the Workprint. Even in 2007 "Final Cut", the obviousness of the error has been reduced, but if you look closely, you can still see that the audio doesn't quite match the visual.
When Deckard asks Racheal if Tyrel's owl is artificial, she replies "Of course it is." However, her lips movements do not match what we hear. This is because when the scene was filmed, actress Sean Young answered the question by saying "Of course not." Director Ridley Scott changed this in post-production because he wanted to establish that Tyrell could make perfect imitations of living things.
In the opening interview with Leon, Leon states: "Let me tell you about my mother..." Later, when Deckard is thinking about the interview (as he drives through the tunnel) Leon is heard saying "I'll tell you about my mother..." This could be attributed to Deckard simply remembering the dialogue incorrectly.
The sheet music that Rachael reads does not match the song that she plays on the piano (not least because it is for guitar). She could, of course, be playing from memory and not referring to the music at all.
In the scene where Rachel pulls down her hair, while in Deckard's apartment after the Leon fight, her hair goes from straight, to very curly. If her hair was truly that curly, the she would have had to pull her hair straight back and very tightly into a bun, in order for her to hide her curly hair. If her hair had been "straightened" with some form of cosmetics or salon treatment, it would have stayed straight after she let her hair down.
When Deckard approaches Tyrell's office in the spinner, the sun is out of frame in the sky, indicating that it's late morning. But when he enters the office, the sun is just below the tip of an angled building indicating early morning. As the scene progresses through about five minutes, the sun progresses normally upward past the tip of the building until the window is darkened. After a time-lapse during which Deckard asks Rachel over 100 lengthy questions involving narrative responses, she walks out of the room and we see the sun is barely out of frame again, indicating that about another five minutes have passed. Not nearly enough time to ask or answer 100 questions.
When Deckard and Bryant are reviewing the video from Leon's VK empathy test, the dialogue between Leon and Holden is not as fast as it was in the original scene. In addition, Leon is heard to say "Uh..." prior to identifying his hotel room number, which he does not do in the earlier version of the scene.
When Pris meets Sebastian, the visible words on the marquee on the Million Dollar Theatre change from "Andres Garcia...Vidas" to "Los Mimilo Co..Mazacote Y Orque" (Corrected in the 2007 "Final Cut" of the movie; the word are consistently "Andres Garcia...Vidas").
When Deckard is in his apartment examining the photograph of Rachael as a young girl with her mother, two photographs are shown. The first is a physical photograph that Deckard holds in his hands, the second is a supposed close-up of the same photo that comes to life for a brief instant. The position of the shadows in the shots show they were captured at slightly different times of day.
When we see Deckard waiting for his noodles, he is reading that day's newspaper. Later in Leon's apartment, the same newspaper is seen in one of the drawers, except it is old and soiled, as if it has been there for years. We know they are the same since both newspapers have the same headline about farming on the moon.
In Leon's apartment, right after Deckard enters the bathroom for clues, Gaff is outside playing with a matchstick and the apartment entrance door behind him is closed; but when Deckard comes out of the bathroom and looks at Gaff finishing his sculpture, the door behind them is wide open with blue neon light streaming in.
This mistake is from the Spanish dubbed version: When Deckard is talking with Bryant while they see the Leon's interview made by Holden, in the Leon's profile appears the birth-date: April 10, 2017. Later, when Deckard fight against Leon in the streets, he says: "Nací el 2 de Abril de 2017".
When Deckard is being chased by Batty through the Bradbury building, there are two shadows visible on a wall; the shadows belong to director Ridley Scott and cinematographer Jordan Cronenweth (this has been corrected for the 2007 Final Cut; the shadows have been digitally removed).
Roy Batty and Leon enter "Eye World" to interrogate Hannibal Chew. As the sliding door to the room opens, you can clearly see a set lighting stand leg in the lower left of the opening. This was not caught in the newest version of the film.
During the fight scene between Deckard and Leon there's a point where Deckard gets thrown into the windshield of a car. However, when he is thrown and still in the air you can clearly see the windshield is already smashed with the imprint of his body, before he ever hits the actual glass. According to Paul Sammon however, this is not a goof - the window is broken because the car is supposed to be a derelict, not due to a continuity error.
When Deckard performs the Voight-Kampff on Rachael there is a bellow measuring her breathing, yet we do not see Deckard attach it and there was no such apparatus attached to Leon. (The bellows are designed to collect invisible airborne particles emitted from the body, as mentioned in the original 1982 Blade Runner press-kit.)
The glass that Louie hands over to Deckard has a different shape than the one that Deckard takes a sip from in the following shot. But there are enough shots of other patrons in between to suggest the passage of time. Even the 8 seconds or so of real time the shots occupy, might be enough for a veteran drinker to down one and order another.
Bryant tells Deckard that six replicants escaped from an Off-World colony. One was killed trying to break into Tyrell's, and the others escaped. However, there are only four replicants in the film (Roy, Leon, Zhora and Pris); if one goes by Bryant's dialogue, there should be five. This infamous goof has been corrected in the 2007 Final Cut where Bryant now says that two replicants were killed trying to break into Tyrell's.
Support cables for spinner are clearly visible in the shot where Deckard and Gaff take off after Gaff has told Deckard that Bryant wants to see him (corrected in the 2007 "Final Cut" of the movie; the wires have been digitally removed).
When Roy Batty, and Leon enter "Eye World" to interrogate Hannibal Chew, the environment is supposed to be so cold that it will kill Hannibal without his protective suit, yet there is water dripping from the icicles on the ceiling.
When Deckard finds Zhora in the back room of the photograph, and zooms in on her face, the person he sees is clearly not Joanna Cassidy (the actress who plays Zhora). Additionally, when he prints out the close up of her face, the hard copy is at a completely different angle to the image on screen. The first goof was corrected in the 2007 Final Cut; the image on screen is now that of Cassidy. The second goof however remains.
A hand is visible on Batty's shoulder while he is supposedly alone in the phone booth. This is because the shot of him looking up and smiling is a flipped shot from later in the film when he meets Tyrell, just prior to saying "Nothing the god of biomechanics wouldn't let you into heaven for" (corrected in the 2007 "Final Cut" of the movie; the hand has been digitally removed).
Between the Director's Cut and Final Cut Deckard's bruise on his face is removed to correct an amended story line. However Deckard still uses a handkerchief to dab blood away from his lips caused by the yet to happen encounter with Leon (later on he swills the blood out of his mouth which would originally have matched up with this).
When the street vendor is examining the snake scale, the serial number she reads out loud doesn't match the number on her video screen (corrected in the 2007 "Final Cut" of the movie; the graphic now matches her dialogue). Additionally, she never removes the scale from the plastic bag in which it resides when Deckard gives it to her. There is no conceivable way that any microscope could produce such a clear image through plastic.
The goof items below may give away important plot points.
When Deckard is in Zhora's dressing room there is no tattoo on her left cheek, as is seen in the photograph printed from the Esper. It is first seen when she is in the dryer. After that, it appears (darkness varies) and disappears throughout the scene. It is most prominent when her body is rolled over after Deckard shoots her.
After retiring Zhora, we see Deckard with a cut on his right cheek as he buys a liquor bottle. But when Leon pulls him aside, it vanishes. Then right after this fight, Deckard's cut reappears. This is because his purchase of the bottle was shot to take place after the fight with Leon (if you look closely behind him, you can see that Rachel is waiting for him about ten feet behind him), but during editing, it was switched to before it - thus creating the continuity error of the scar (corrected in the 2007 "Final Cut" of the movie; the scar has been digitally removed).
In the final sequence on the rooftop between Deckard and Batty, Batty releases a bird he is holding while it is raining. When we cut to a shot of the bird flying away, the bird is not flying in rain, the sky is cloudless. Additionally, the building alongside which the bird flies looks nothing like the Bradbury building. Director Ridley Scott has admitted that when he filmed the rooftop scene, he was unable to get a proper shot of the bird flying due to the rain effects employed during the shoot (doves do not fly in wet weather). Consequently, the "dove-flying-away" sequence had to be shot at a later date completely different weather and beside a completely different building (Corrected in the 2007 "Final Cut" of the movie; digital effects have been used to match the sky to the weather and the building to the roof of the Bradbury).
At the end of the Zhora chase, Deckard fires four shots from his pistol as Zhora runs directly away from him, in line with his shots. His first two shots miss her; the second one as she breaks through a plate glass window. His next two shots both hit, but both pass through her shoulder and continue out in front of her. All the glass windows in her path should have been shattered, but none are.
Despite being flung against several solid objects and smashed onto a windscreen, there isn't a single mark on Deckard's torso when he is cleaning up after the fight with Leon. The only result of the fight seems to be a little blood in his mouth. However, if Deckard is a replicant, his lack of injuries would make sense.
The opening scroll seems to imply that the Blade Runner unit was formed as a reaction to the Nexus 6 replicants, but in the movie itself it is made clear that the Blade Runners like Deckard precede the development of the Nexus 6 (seen when Bryant has to tell Deckard about the 4 year life span - if the Blade Runner unit had been created specifically to deal with Nexus 6's, Deckard would have known this information). This may be an indication that Deckard is a replicant.
Early on when talking to Bryant, Deckard is surprised/puzzled why the replicants risk coming back to earth and finds it unusual. This was his previous job, and he's apparently good at it, which is why they want 'the old Blade Runner' back. However, some fans see this as evidence that Deckard is in fact a replicant.
When Zhora crashes through the glass walls, the trigger for the blood packs can be seen in her right hand as she raises her two arms out in front of her, as well as the line snaking through her clothes.
There is an obvious stunt double in the scene where Zhora crashes through the glass walls. This was corrected in the 2007 "Final Cut" version. Joanna Cassidy was brought in to re-shoot the stunts wearing the same costume and using green screen and digital manipulation to replace Lee Pulford's (the stunt double) head with that of Cassidy's. If you look very closely at the shot of Zhora as she stands back up after tripping, you can see that Cassiday has aged.
During the scene in which Batty inserts the nail into his hand, you can see he already has wounds from a later scene in which Deckard hits him with a pipe (his torso and head are both covered in blood). The tilework on the wall next to him reveals that it is the same room that the later fight takes place in. Additionally, the window is broken, although the scene where we see how it was broken has not happened yet.
In all versions of the film other than the 2007 Final Cut, in the scene where the character Roy is introduced, he clenches his fist and you can see the nail from the end of the movie in the back of his hand.
When Deckard and Pris are fighting in Sebastian's apartment, she is played by a stunt double in some shots. In some we see Pris clearly wearing nude pantyhose that give her legs a matte look, while in other shots her legs are bare and shiny with sweat.