When Rizzoli goes into a shop to buy a sandwich it is nighttime, but when she arrives home with the sandwich you can see through the windows of her house that it is daytime outside.
At the end, when Rizzoli comes out of the sporting goods store with the rifle, she is holding her badge in her right hand displaying it so people can see that she is a cop. After the scene cuts away and then back, the badge is no longer in her hand, but on her right shoulder, attached to her holster.
When Rizzoli and Marshak try to get out of the window, they are blocked by bars. Moments later, Earl comes crashing through the same, but now bar-less window. Then Leo and Earl flee through the same bar-less window, pursued by Rizzoli and Marshak.
When Whoopi breaks into Kroll's home and catches him swimming nude with nothing but a gold swim cap, it is noticeable that the actor was wearing a gold-colored speedo-type swimsuit for the medium shot.
When Delgadillo says "Look at this. They even stamped the package wrong!" his mouth doesn't match what he is saying.
Earl Skinner switches the jungle style clips on his Ruger AC556K three times during the final shootout. Essentially loading his gun with an empty clip before he tries to shoot a pinned Rizzoli.
During the bust before the shoot out with Skinner, Carl is uncharacteristically negligent in his duty to protect and serve when he fails to explain to those kids the reason he's confiscated their stash is because it's poison, and shoos them off, leaving them to think it was just because it was illegal. Then if Rizzoli's plans to terminate the dealer fell through, and he survived, those kids risked buying poison from him again, rather than at least learning to vet their dealer better.