Continuity mistake: When Selene dodges the flamethrower, her boots go from heels to flats, only to return to heels moments later. (00:06:00)
Continuity mistake: At the beginning, when she first unfreezes after her capture she is naked and looks toward her corset and boots in a medicine cabinet. She breaks the glass for the boots first and grabs them. We then see her breaking the glass for the corset, but the boots are still in the glass next to the corset in the lower left-hand corner. (00:09:55)
Plot hole: Selene has been kept in a cryogenic tank for 12 years. And for 12 years the scientists running experiments on her very conveniently kept her boots and skin tight suit in the lab. Not just that: they did not keep them in a locker or in a box, but scattered across different shelves of the glass cabinet where they also store test tubes and big bottles of chemicals. Directly in front of them, in fact. (00:10:00)
Continuity mistake: When Selene escapes the facility at the beginning of the film and slashes some of the guards' throats with a scalpel, she leaves a ton of blood on the floor and walls, as well as a trail of blood as she slides across the floor. But moments later when we see the bodies on a security camera, all of the blood has disappeared. (00:11:55)
Continuity mistake: Selene holds an Antigen scientist in his apartment against a huge window by her left hand and asks about Subject 2. The man tries to break her grip and has his two hands around her wrist. The position of the hands differs between shots showing his face and shots from the side. (00:20:50)
Continuity mistake: In the secret covenant, the amount of blood on Eve's white top decreases when Olivia the vampire doctor examines her wounds. This is most noticeable under the collar. (00:34:20)
Revealing mistake: Right at the end of the fight between Selene and the Uber-Lycan in the vampire coven, the Uber-Lycan throws Selene into some wooden panels, knocking her unconscious. As she travels through the air you can tell that she is suspended by wires; she travels far too slowly towards the wooden panels for someone who was just thrown. (00:48:35)
Visible crew/equipment: When Detective Sebastian is talking to Selene about his wife who was killed in the purge, watch the buildings in the background as he says "she told me she loved me, and then she let the sunlight in". The vehicle used to tow the car that they're sitting in and the camera rig are reflected in the buildings' windows. (01:00:20)
Factual error: Detective Sebastian fires a total of 7 rounds at the Antigen van in the parking garage - three at the driver, two at the front-left tire, one right before the van nearly runs him over and then one after it passes him - without reloading, yet the Taurus Judge revolver he is using is designed to only hold 5 rounds in its cylinder. Later, after Sebastian has reloaded the revolver, he fires 8 rounds at Dr. Lane, again without reloading.
Continuity mistake: When Selene gets to the parking garage, she is wearing her skin tight outfit and is only armed with her guns. But from out of nowhere, she suddenly pulls out a grenade. Her outfit has no pockets and it was not attached/hanging from her outfit.
Continuity mistake: When Eve wakes up, her white dress has no blood on it. In the next shot, her white dress has blood on it again.
Other mistake: Throughout the saga, blood has been shown as essential for vampire's healing factor, and Selene herself used her blood to heal people. Somehow, this time around neither her or her pal David think in any way of this basic fact, making a complicated trip to the vampire doctor necessary, who simply feeds the vampire kid some blood, the very first thing any vampire would do to regain strength.
Continuity mistake: Last scene of the movie on the roof Selene goes through her prologue looking out at the city and she has a bloody mark over her left eyebrow. Eve reaches for her hand and she looks down; when she looks back up the bloody mark is gone.
Visible crew/equipment: After the car chase is over and Quint pulls up and looks at the dead Lycan, as he pulls away you can see the reflection of the camera.