When Bell changes the magazine of her HK MP5 during the firefight in the bank, the sub-machine gun's safety is set to S (Sicher = Safe). During magazine changes (especially under fire) you leave it at the setting that you had: E (Einzelfeuer = Single Shot) or F (Feuerstoss = Full Automatic).
In scene where Kidman sits on town wall to talk to her daughter, Shelby's boyfriend (Toby), as shot changes between his and her look at one another, passers by in background do not match: first striped clothing woman walking towards them, from Toby P.o.V. to Kidman, approaching, back to instant Kidman P.o.V. of Toby, she is already walking away: next, blue-suited man with briefcase walking past Toby (from Kidman P.o.V.): next shot of Kidman, he does not pass: two further shot changes, one to Toby, then back to Kidman (some minute+ passing) and suddenly, now there he having passed by in background to Kidman.
The goof item below may give away important plot points.
In the opening scene, the police noted the gun had no prints and no serial number, yet the gun appeared to be lying in place on the ground. Fingerprints are ultimately processed at a crime lab, or at least require dusting of the object. It is later shown that Bell did not care to not wear gloves, and at that point was dying and not seeking medical care.