Continuity mistake: When K is approached by the replicants at the food court, there is a tin on the table in front of him. The lid has been removed from the tin, and then placed on top of it at a rotated angle. In a close-up shot of the table, the lid on top of the tin is positioned at a different angle. (00:44:25 - 00:45:10)
Continuity mistake: When Coco is examining the skeleton, Lieutenant Joshi is leaning against the medical table with her elbow a couple inches away from the skull and upper torso bones. A couple of shots later, when the camera focuses on the bones, Joshi's elbow is not against the table. Then in the next shot, her elbow is back again. (00:24:30)
Continuity mistake: When Wallace slits the newborn replicant's stomach, he places his hand on her cheek, but in the next shot, his hand is suddenly on her shoulder. (00:41:45)
Continuity mistake: When Luv confronts Lieutenant Joshi in her office, in the shot where she switches off the computer monitors, there are a series of files on her desk in front of the monitors. There is a white file, next to it a black file, and next to that a beige file with two files under it. When Joshi stands up, the beige file and the files under it have gone and there is now a gap between the white and black files. Later on in the scene, after Luv picks up Joshi's body after stabbing her, the black file is on the left, the beige file is back and in the middle, but no files under it, and the white file is on the right. (01:38:00 - 01:40:05)
Continuity mistake: When Dr. Badger has finished analysing the wooden horse, he takes it off the scanner and holds it in both his hands, whilst still facing the scanner. The shot cuts to Dr. Badger giving the horse back to K, and he is suddenly holding the horse with one hand, and is facing K's direction. (01:34:55)
Continuity mistake: When Luv strikes Coco on the back of the neck, on the floor he is bleeding from his nostrils, a tear streak of blood is shown coming from his eye, and has blood spewing from his mouth. There is a shot of Luv for a few seconds in between these two shots, but the amount of blood that Coco is shown producing appears far too quickly for just a few seconds. (00:49:55)
Continuity mistake: When K discovers the 6 10 21 marking on the root of the tree, the scene cuts to a wide shot where his car is shown parked to the right of the tree. When K walks back to the car, the car is suddenly parked to the left of the tree. (00:49:05)
Continuity mistake: When K finds the metal case in Sapper Morton's piano, after closing the piano lid, he is holding the case in his hands, with two fingers on his right hand pressed against the side of it. The shot cuts to another angle, where the two fingers on his right hand are now suddenly behind the case. (00:47:10)
Continuity mistake: When Sapper Morton is fighting K, he pushes him into the wall, causing the wall to break and the two fall through it. The damage from the wall leaves rubble scattered on the floor around them. Sapper begins to choke K, and the rubble surrounding them changes position when the shot cuts to a closer angle of K. (00:08:15)
Continuity mistake: When Sapper Morton is in his protein farm, he begins to stand up when finishing, but in the next shot, his hands are suddenly reaching back into the water. (00:03:10)
Continuity mistake: When Wallace tells Deckard "Pain reminds you the joy you felt was real", Deckard rests against the back of the chair he is sitting in. The light above them moves away from Deckard, leaving him shadowed, but when the shot cuts to an angle behind Deckard, the front of his face is suddenly covered in light. (02:14:15)
Continuity mistake: When K fires at the scavengers in the scrap yard, he keeps his gun pointed at them and an additional group of scavengers runs over a hill in the background. The shot cuts to an angle behind K, with his arm lowered, but in the next shot, his arm is suddenly raised and aiming again. (01:03:00)
Continuity mistake: When K is getting out of his car after the scavengers break the door open, he struggles to stand, holding onto the side of the car. One of the scavengers then runs up to K, next to the car. K then fights back and he is suddenly standing upright, several meters away from the car. (01:02:45)
Continuity mistake: After examining the skeleton, Coco gets up from his seat and K starts to walk towards the console to examine the skeleton himself. When K begins to walk over to the console, Joshi has her arms by her side, but in the next shot, her arms are suddenly crossed. (00:25:50)
Continuity mistake: When Coco is examining the skeleton, the shots of Coco in focus show Lieutenant Joshi in the background leaning her elbow on the medical table, and remains this way until Coco says "Sorry" after referring to Sapper Morton as a sentimental skin job. Joshi then asks where's the kid and she suddenly has her arms crossed and not leaning on the table. This isn't very easy to see when she is asking, but is noticeable when Coco gets up from his seat in the next shot. (00:25:35)
Continuity mistake: When the LAPD are looking over the bones, there is a shot of the teeth from the skeleton being placed on a table one at a time. The shot cuts to another angle of the table to focus on the hair sample, and the part of the table where the teeth have been placed is still visible in shot, but the teeth are suddenly nowhere in sight. (00:24:05)
Continuity mistake: When K is at his apartment, Joi lights his cigarette which smokes slightly. The shot cuts to a different angle, and there's much more smoke. (00:18:20)
Continuity mistake: When K is ambushed by the scavengers, the first one attacks him and K breaks his back with his knee. A second one then attacks him and K drops the first. When the first is dropped, the body is positioned near the car. Seconds later, when K is blasted back by an explosion, the first scavenger that attacked K has moved more ahead of the car. Also, when Luv is shown watching K from her perspective, the first scavenger's body has now moved again, several meters away from the car. (01:02:50 - 01:03:50)
Continuity mistake: When K frees Deckard from his restraints after drowning Luv, K pulls Deckard out of the water with his right hand, grabbing onto Deckard's shoulder. In the next shot, K suddenly has his right hand on the ceiling of the car. (02:25:45)
Continuity mistake: K is shown to have a very thick stubble beard throughout the movie, but when he returns to the LAPD for his second baseline test, it is notably thinner than before. (01:16:35 - 01:23:05)
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.