Continuity mistake: When K is cornered by the scavengers, he gets out of the car after they cut the door open. In the shot of one of the scavengers running up to K to attack him, nothing is hanging out of the car door. K then breaks the scavenger's back with his knee and the seat belt is suddenly hanging out of the door. (01:02:45)
Other mistake: It is established in the movie that whenever Joi is switched on through the emanator, or when she tries to communicate with K when switched off, a chorus line from the song Peter and the Wolf will play. This is shown at numerous points: when K first activates the emanator, when K is talking with Luv at Wallace Corporation, when K is talking with the hooker, when K switches her on when he is analysing the DNA, when she is reset after the car is shot down and when she switches herself on to tell the hooker to leave the apartment. However, when Luv is beating up K, Joi switches herself on to tell Luv to stop, but the chorus line from Peter and the Wolf is not heard, despite being heard every other time in the movie. (02:00:30)
Deliberate mistake: When Deckard wakes up in Wallace Corporation, there is a wide shot of the platform he is on. All four corners of the platform are empty in the wide shot. Deckard then looks at Wallace's visual aids as they float away, and then realises Wallace is standing in the corner directly facing where he is sitting, speaking to him. This corner was empty in the wide shot, with no sign of Wallace. Wallace could not have entered in between shots because Deckard would have seen him approaching or at the very least, heard his footsteps. This was likely done intentionally as to not give Wallace's reveal away too early. (02:08:55)
Audio problem: Just after K finds the 6 10 21 marking on Sapper Morton's tree, he begins to head back to his car. In the shot from behind K where he is first walking to the car, the only sounds heard in the shot are his footsteps and nothing else. The shot then cuts to an angle behind the car with the door opening, and it is now shown that K has set Sapper's house on fire, and the sound effects of the flames burning are suddenly heard. The sound of the flames burning the house should have still been heard in the shot where K was walking up to his car as the house was already on fire. (00:49:15)
Continuity mistake: After K destroys the two other cars, Luv runs up to the front of the car to see out the front window. She places her left hand on the driver seat, with her hand touching near the bottom of a metal plate attached to the side of the seat. The shot cuts to a different angle, where he hand is now touching most of the metal plate attached to the seat. (02:20:05)
Continuity mistake: When Luv walks over to Wallace to with a box of devices to access his visual aids, Wallace places his left hand on the top of his leg. Luv then slides open the box, and Wallace now has his left hand closer to his knee. (00:39:30)
Continuity mistake: When Wallace is looking at the newborn replicant with his visual aids, in the shot where he says "A child can count to nine on fingers", the corner of the towel that the replicant was covering herself with is on the floor. The shot cuts to a different angle, where he says "We should own the stars", and the corner of the towel is now more ruffled than it was in the previous shot. (00:40:45)
Continuity mistake: When Mariette is standing in the street with the two other replicants, there is a woman to the right of shot, wearing some sort of mask and goggles on her face. She is holding an umbrella, with the pole facing the right hand side of her head, but in the next shot, the pole of the umbrella is now facing the left hand side of her head. (00:43:55)
Continuity mistake: Whilst the giant Joi is chatting up K, there are streaks of wet blood shown going down his neck due to his injuries getting rained on. These wet blood streaks continue to grow for the next thirty seconds. When he takes off the bandage over his nose, the wet blood streaks on his neck have disappeared. (02:17:12 - 02:17:55)
Continuity mistake: Whilst K is being walked through the orphanage by Mister Cotton, he stops when he recognises an area from his dream. In a shot from behind him, he is shown turning his head to the left to look at the area, but when the camera cuts to a different angle of him, he is looking straight forward, and then turns his head to the left a second time. (01:09:00)
Continuity mistake: Whilst Luv is in a meeting with a buyer, she suddenly gets a message alert. She is holding a cup of tea in her right hand and holding a saucer in her left. She then lowers the cup back onto the saucer without taking her hand off it, but when the camera cuts to a wide shot of the room, both hands are suddenly touching the saucer. (00:30:40)
Continuity mistake: When Luv is first introduced, she is shown pouring tea into a cup placed on a saucer and then raises the saucer. In the close-up of her hands and the cup, her left hand is completely shadowed. The camera then changes angles and half of her left hand is suddenly covered in light, with the other half shadowed. (00:30:30)
Continuity mistake: K gets into his car after taking out Sapper and picks up a police report card from the dashboard to fill out. Whilst the car voice is heard saying "Incoming LAPD re-codec hash", K picks up a pen and places his right hand over the front of the report. His fingers are placed flat on top of the card when he does so. But then it cuts to a close-up shot of the card, where his fingers are now curled and the side of his hand is placed against it. (00:10:35)
Continuity mistake: Just after K has finished scanning Sapper Morton's eye, he stands up and says "Please don't get up" to him. The shot then cuts to Sapper lying on the floor and his right lower arm is raised. It then cuts to a wide shot of the room and Sapper's right arm is suddenly on the floor. (00:08:59)
Continuity mistake: When Mariette is with K in the replicant hideout just after he wakes up, there is a moment where Mariette is shown placing her hand on the side of K's face. It then cuts to a shot focusing on Mariette, where her hand has moved down to the side of his neck. (02:04:00)
Continuity mistake: When Luv swims back to the sinking car, the exterior shot shows her placing her left hand on a seat in front of her. The shot then cuts to inside the car, where it is now her right hand placed on a seat that is to her right. (02:24:00)
Continuity mistake: When K swims back to the sinking car to stop Luv and rescue Deckard, K grabs Luv and pushes her up against the ceiling. There is a shot outside of the car looking inside the car, where K has his hand around her neck and is holding onto the side of her face. It then cuts to Luv where K now has his hand entirely around her neck. (02:24:10)
Continuity mistake: When K and Deckard are standing outside Dr. Stelline's facility, Deckard asks K "who am I to you?" and K turns his head to face Deckard. The shot cuts to K, where his head is suddenly slanted at an angle. (02:29:15)
Continuity mistake: Just after Luv throws herself and K out of the car after he attempts to rescue Deckard, the two land in the water rising up against the sea wall. When Luv first kicks K, he is kneeling on the ground attempting to stand up. The shot then cuts to a different angle, where K is suddenly standing mostly upright. (02:22:20)
Continuity mistake: When Freysa is speaking with K, she raises his gun so that it is pointed at her. Just after she says "Dying for the right cause is the most human thing we can do", when the shot is on K, he lowers the gun slightly and it goes out of frame. It then cuts to a shot focusing on Freysa, where the position of the gun remains the same and doesn't change. The shot then cuts back to K at the same angle, where the gun is now visible at the the bottom of the frame, even though the gun didn't change position. (02:06:25)
Answer: Think of any manufacturing process. Samples of new products are frequently created and then immediately destroyed. Also, the new replicant would require processing, training, etc. It was simpler for him to just dispose of the test.