During the flashback scene in which a Terminator infiltrates the underground human hiding place and starts killing people, if you look at the right side (his right side) of the Terminator's face by his eyes, you can see a flat line which is part of the makeup used to give him his glowing red eyes (like the sunglasses with LED lights that were popular to wear in the 1980's).
When the Terminator tosses the bearded man away from the phone booth and begins searching the phone book for Sarah Conner, he uses his finger sliding down the page to assist separating the lines of type, the way human beings do when they read. Yet the Terminators have specially enhanced telescopic vision that allows them to zoom in/out, etc., on anything, even in the dark. It therefore makes no sense that this Terminator would have to use his finger to assist with his reading, he should be able to merely glance at the book and zoom in on the entire page, or on the smallest part of the page and process this information in seconds.
Before the TechNoir scene, Reese pumps his shotgun at least twice, which would load a shell into the chamber and make it ready to fire. But when he identifies the Terminator at the nightclub, he has to pump the gun again before firing.
During the scene where the psychologist is talking to Reese, the attending police officer in the interrogation room has his sidearm on his hip. Police officers don't wear their sidearms when in an interrogation room with a suspect.
When Det. Vukovich laughs at Dr. Silberman's ray gun joke, he can be seen reacting to an off-screen crew member who must be gesturing for him to stop looking at Sarah Connor and back to the video monitor.
When the Terminator is stalking Kyle and Sarah in his police car, the sticker on the driver's door reads "To care and protect". When the car is later wrecked in a tunnel, the sticker has changed to "Dedicated to serve".
As Kyle and Sarah are sneaking toward another car in the parking garage, a police car with the serial number 1874 drives by. The number 1874 is also visible on the Terminator's police car. The first car that drove by couldn't have been the Terminator's because a second cop is visible in the passenger seat.
The number 14239 appears above the front door of the first Sarah Connor (a similar number 14329 appears above the entrance of the Alamo Gun Shop) but does not match any of the addresses for Sarah Connor shown in the telephone directory.
When Sarah is first holding the iguana, she is holding it across her body, the shot then switches to a head-on and the iguana is resting on her shoulder. It then switches back to it's original position.
Just before the Terminator crashes his car through the police station door, the officer is writing on a form with his left hand on the table. In the next cut he has his left hand on the form. The position of the pencil also changes in the two shots.
When Sarah tries to escape from Reese in the first car chase, he grabs her by the hair. His grip on her (grabbing her hair, pinning her to the seat with his arm, shoving her head to the floor, or not holding her at all) changes frequently during the chase.
At the beginning of the film, when Reese aims a gun at the police officer and demands to know the date, the officer tells him it's May 12. The first scenes with Sarah, which take place later that same day after sun-up, show her clocking in at the restaurant where she works. The date on her time card reads May 19.
After the Terminator finishes operating on himself and puts on the sunglasses, he only has a shirt on, but when he walks towards his bed to get the guns from underneath the mattress, he is suddenly wearing a leather jacket.
When Reese tosses the third pipe bomb, we can see that the pick-up and motorcycle are almost at the end of the tunnel. But when Reese tosses the fourth bomb, the two vehicles still have a long way to go. After the fourth bomb explodes, the truck and motorcycle have cleared the tunnel.
When the Terminator gets into the tanker truck, there is a close-up shot of his left hand grabbing onto the type of door handle that protrudes from the door, and pushing the button on the handle with his thumb. But when the Terminator is chasing Sarah and Kyle with the truck, the door handle is the rectangular type that is recessed into the bottom right corner of the door.
When the Terminator kills the first Sarah Connor, he comes through the door and extends his gun arm fully. After a brief cutaway he fires, but he is now behind the door frame and his arm is in a different position.
In the first two car chases between Reese and the Terminator, Reese's headlights are turned off. What's more, when Kyle Reese steals the second car from the parking garage, he again doesn't turn the headlights on. When we see the car exit the parking garage, the headlights are on. But when we see the car again, the headlights are off again.
In the shootout at the police station, the Terminator twitches in response to being shot while taking out the building's power supply, yet is not phased at any other point when he's shot, including by the police officers armed with M16 rifles.
When Reese starts his explanation in the Ford LTD, he appears to have a brand new wound under his lower lip. When he continues his explanation in the other car (which is only a few minutes later) the wound has been healed and replaced by a scar.
In the parking garage, when Reese and Sarah get into the car to steal it, Reese's coat gets caught in the door of the car and is pulled tight enough to restrict his movement. A moment later, the coat is free and loose around his neck.
In the TechNoir scene, when Sarah Conner sits down, there is no Canada Dry drink in hand. Seconds later, during the same "You've got me Burning" song that is playing in the disco, the bottle is in hand.
When Traxler and Vukovich arm up with assault rifles during the police station massacre, an officer with a shoulder rig is seen behind them grabbing his own M16. Later, when the station is on fire, the Terminator steps over the same officer dead on the floor, armed with only his revolver.
When the tanker truck runs over the Terminator and comes to a stop, the driver gets out to check on him while the passenger waits in the cab. The driver however doesn't close his door and the door fails do so on its own. After the Terminator kills the driver, he opens the door and commandeers the truck. Who closed the door? There's no reason for the passenger to have done it.
In the Tech Noir club, the Terminator passes by a woman on the dance floor wearing an orange shirt. A few shots later, when the Terminator focuses on Sarah, the same woman can be seen in the background sitting at a table and talking with friends. There wasn't enough time for her to move.
Both Reese's and The Terminator's outfits change inexplicably throughout the film. Reese first steals a pair of trousers and then a long gray coat and a pair of sneakers, but in the next scene he is shown also wearing a T-shirt. The Terminator wears a military style jacket for the first part of the film, but when he returns to the apartment to "operate" himself he is wearing a leather jacket which he keeps wearing for the rest of the film.
In the tunnel after ditching the car Sarah realizes that Kyle is wounded and dresses his wound, which Kyle comments on as being a pass-through wound. After spending the night in the tunnel, upon leaving, the bandage has no blood on it. Yet, later, after Kyle returns to the motel with supplies, they bandage is saturated with blood.
Both Sarah Connor and Lt. Traxler state that the Tech Noir nightclub is on Pico Blvd. When Kyle and Sarah leave the nightclub, they briefly run down an alley, steal a car and flee the scene. As they leave, a policeman radios in a request for "an ambulance at 7th and Broadway" (erroneously thinking the Terminator will need medical attention). But in reality, 7th and Broadway is nearly a mile away from Pico Blvd. in Los Angeles, not nearby as would have to be the case for the movie sequence to make sense.
The Terminator purchases firearms at a gun store, including a short-barreled, automatic Uzi. There are strict federal laws, and California has had bans on these for decades. No gun store sells them, and no criminal enterprise would have them readily visible on the wall. Converting a long barreled semiautomatic Uzi to full auto takes completely different internal parts, a machine shop and precise tooling.
May 19th in 1984 was a Saturday not a Friday. (This error was due to the script of the film being written in 1983, and the film itself was to begin production that same year, but ultimately was postponed because of Arnold Schwarzenegger's commitment to finishing another project at the time. When it was decided to have the film set in 1984, the writers chose not to change the day of the week.)
In the future human hideout, some children are watching a hollowed-out TV with a fire burning inside it. But even a small fire would cause heat accumulation at the top of the cabinet which would melt and/or ignite it within minutes.
During Reese and Sarah's car swap from the Ford LTD to the Eldorado, Reese hits the ignition with the butt of his shotgun and the ignition tumbler suddenly loosens. This is impossible. Reese would have only knocked the chrome fob off. The tumbler itself can only be removed if a hardened bolt is removed that is inserted through the tumbler itself that both locks the tumbler in place and stops the tumbler itself from twisting when you start the car.
When Sarah is in the night club she has to put change into the pay phone to call 911. While 911 calls are free, many pay phones in the 1980s required you to insert a coin in order to obtain a dial tone.
The three "Sarah Connors" are listed in different sections in the phone book when Reese, The Terminator and Sarah Connor look them up (right page, left page, right page). They might have been different editions, though books at pay phones are generally all replaced at the same time.
After Reese and Sarah Connor flee the police station,
Reese is bleeding from a bullet fired by the Terminator. While the car's windows were not broken during the gunfight, the driver's window is either rolled down or missing, and he could easily have been hit through it - or indeed he may even have been hit by a stray bullet while making his way through the police station, which, throughout the Terminator's attack, is riddled with gunfire.
Traxler allows Sarah to take a nap on the couch, and he tells Sarah her mother should arrive from Big Bear in about an hour. Shortly after, the Terminator arrives, and Sarah and Reese flee, all of this happening at night. Later, the car Sarah and Reese take runs out of gas, and they spend the night under a bridge. A short time later, it's light out, or the next day, and they make their way to the Tiki Motel. Sarah then gets on the phone, and we find out the Terminator is there, and has killed her mother, mimicking her to get Sarah to reveal her location. The question is, why would Sarah's mother still be at the cabin in Big Bear when she was supposedly on her way to pick up Sarah at the police station? No mention is made of her stopping along the way at a pay phone to call her, and there were no cell phones in 1984.
Reese and Sarah ditch an AMC Gremlin after the police station massacre, and they then sleep under a bridge nearby. Despite possibly being exhausted, it seems like they're leaving themselves open to attack by the Terminator by leaving the car in the nearby woods, then sleeping near it. The Terminator could certainly have decided to travel down the same road they did, and possibly have found them.
During the police station massacre, just before the Terminator shorts out the lights, he shoots a policeman in the back. The policeman is clearly seen smiling just before he starts to flee from the Terminator.
During the police station massacre, the camera is positioned on the floor, and shows the Terminator shooting through a door on the left. As he fires his gun, the supposedly dead cop in the foreground can be seen to jump.
After Kyle appears in an alley after traveling through time, he steals a pair of pants from a wino in the alley. Kyle has a slim, athletic figure, and the wino is a large man with a big waistline. Yet the pants fit Kyle perfectly.
When the Terminator gets on the motorcycle to chase after Sarah in the pick-up, he turns on the ignition key and jumps up on his right leg to kick start the bike, but you hear a electric starter motor instead before he rides off.
When Sarah and the Terminator are crawling through the hydraulic press, the top of the press can be clearly be seen wobbling like plywood in the background lighting. This is the same press that is strong enough to crush the robot by the end of the scene.
When the Terminator examines the Spas-12 shotgun in the gun shop he pulls back the bolt and takes aim, then the camera switches to the store owner (Dick Miller) during which we hear the "click" of the Terminator dry-firing the weapon, then the camera switches back to the Terminator revealing the weapon is still cocked meaning he did not actually dry-fire the gun. The click was added later during editing.
When the Terminator is done operating on his own eye, he has a robotic eye. As soon as he puts his sunglasses on, Arnolds eyes are back to normal and clearly visible through the glasses from that moment on.
The message on Sarah's answering machine goes, "Hi there...
Ha-ha, fooled ya. You're talking to a machine..." with a pause between "Hi there" and "Ha-ha". When the Terminator has shot Ginger, the answering machine starts and we hear the words immediately following each other. Also, when the police call Sarah's apartment, the message changes/speeds up; it is much quicker.
The events from the time Sarah and Reese arrive at the hotel until the love scene are all during the day. In the middle of this Sarah calls her mom's cabin and talks to the terminator. The shot of the cabin is at night, as is the following shot of the terminator riding his motorcycle. Then everything is daytime again until he arrives at the hotel.
The phone number that Sarah Connor gives the Terminator (impersonating her mother) for the Tiki Motel, where she and Kyle are staying, is 408-555-1439. However, after the Terminator hangs up with Sarah, we see him dial 555-1639 and get an answer from the Tiki Motel.
We see Ginger walking back to the bedroom with a plate of food and a glass of milk. When Matt crashes through the door, Ginger tosses and drops the food. When Ginger is shot and is trying to crawl away from the Terminator, the food on the floor in the hallway had some how disappeared.
When Kyle and Sarah hit the Terminator with their truck at the Tiki Motel, the grill has significant damage. During the highway chase, the shots of the front of the truck show no damage to the grill whatsoever.
When the Terminator skeleton rises out of the flames, a silhouette of a crew member can be seen behind the flames, rising from a crouch to pull a big lever. As the lever comes down, the metal skeleton rises up.
When the Terminator stumbles out of the burning cab, he collapses and burns in the fire. Its skull is clearly shown burning with no internal machinery. Later, when it rises out of the fire, it does so from underneath wreckage of the cab. These two inconsistencies have led some to erroneously believe that there was someone else in the truck.