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!
Other mistake: Bryant mentions that 'six skin jobs' escaped and that one got fried trying to get into the Tyrell building. Four of them die in the movie, so what happened to the last one? [In the "Director's Cut" and "Final Cut" versions the math has been fixed. Bryant now says that two of the replicants got fried, not one.]
Other mistake: When Deckard and Bryant are viewing the interview tape showing Leon's interview at the Tyrell Corp they are shown Leon's replicant statistics. The tape shows Leon's model number: N6MAC41717. This designates Leon as a: Nexus 6, Male, Physical Level: A, Mental Level: B, and an incept date of: April 17, 2017. The incept date shown under his model number is: 10 April, 2017. As Deckard and Bryant continue to watch the tape they see the other replicants: Roy, Zhora and Pris with their individual statistics showing a matching model number to their incept dates.
Other mistake: The snake scale changes size and shape each time it's seen, it begins as a large hexagonal shape bigger than Deckard's finger tip when he first finds it, it's later seen as a very small triangular shape in the sample bag and it ends up as a guitar plectrum shaped object when he hands it to the street merchant for identification.
Other mistake: When the woman puts the snake scale under the microscope she doesn't take it out of the bag. She turns on a monitor to view the image; the image when shown is on a different monitor (you can tell by the controls to the right of the image). The image is not a snake scale, it is a marijuana leaf from the Sharf book (his book is in the ending credits).
Other mistake: Just before Leon's questioning starts, Holden turns on the VK and the eye monitor censor piece flips out. There is a view from Holden's perspective showing Leon's eye in on the screen, meaning the eye piece has already zoomed in on Leon's eye. Then just after Leon says "Care if I talk?" it cuts to a side angle as he says "I'm kind of nervous when I take tests." This view shows Leon is looking towards the wall at a 90 degree angle away from the VK, meaning the view screen and eye piece could not have been seeing his eye at a frontal view as show in the previous shot.