Detective McKenna carries a stainless steel Smith and Wesson 5906 throughout the episode, which is seen in a closeup shortly before firing near the end, but when she shoots it changes to a black Smith and Wesson M&P.
At about minute 8:50, while looking at the security camera footage, Nancy says "Chevy body, triple-unit rear-light assemblies; that's a '69 Impala." Again, at about minute 10:05 Fletch says "found your '69 Impala." The Impala shown is not a 1969, it is a 1965. The 1969 Impalas did have triple-unit rear lights, but they were rectangular and mounted in the bumper, not round and mounted on the body as they are on this Impala.
When McKenna plops a cartridge in a plastic bag on the gun shop counter, the owner says, "That a shell casing you got there, detective McKenna?" However, the contents of the bag are clearly a complete unspent round, not just a casing.
Since DMV records belong to the state, a search warrant would not be needed by a police organization to identify the owner of the old Chevy at the beginning of the episode.
Claire states that she froze the cartel's accounts "with two-factor authentication." As an employee of the accounting firm, she would not need two-factor authentication to do this. It might require two separate employees to unfreeze the accounts (depending on the policies of the firm) but two-factor authentication is something used by clients, not employees.
Jessica Alba's gun is shown firing in close-up and extreme slow motion. As the gun fires, the slide moves almost completely back and the cartridge case is shown beginning to eject before the powder burn and bullet begin to exit the barrel. In actual use, the bullet and powder burn will exit the barrel before the slide moves back much, if at all.
In the convenience store shootout, both detectives are seen holding empty guns- the slides are back. This happens after the last round is fired. Instead of immediately reloading, as cops are trained to do, they have a conversation instead.
While this is much more of a comedy than a drama, that error was a significant fundamental one.
While this is much more of a comedy than a drama, that error was a significant fundamental one.