Deliberate mistake: When Frenzy attacks Sam, the teenager wears straight leg jeans with a narrow leg opening (not boot cut) and thick-soled Nikes, seen in numerous shots, as he kicks at the Decepticon. After the cut to Mikaela (who finds the reciprocating saw), during which Frenzy has already pulled off the bottom of Sam's jeans, Sam continues to kick and scream just before he gets up and runs. Problem is Sam still wears both thick-soled Nikes, neither of which slipped off as Frenzy maniacally pulled the jeans, with narrow leg openings, from his kicking legs/feet. Impossible even in the best of circumstances.
Deliberate mistake: During the scene where Carlos and L.J. are searching the motel, L.J. sees a zombie which turns out to be a reflection in a wall-length mirror. L.J. shoots, breaking the mirror and realizing his mistake. But, if he had been standing in front of the mirror as shown, he should have seen his own reflection standing there as well. This was done as an homage to a similar encounter in the original game. (00:24:20)
Deliberate mistake: At the end of the movie, where the girls chase stuntman Mike, they drive the upper dusty road. When their car is shown front outside angle, there's a lot of dust rising from the camera crew's car. But when the camera angle gets into their car and shoots strait ahead - the dust is all gone, the air is perfectly clear.
Deliberate mistake: In the facial morph, the faces don't come anywhere close. The face was morphed with no feature of either resembling the other. The only matching features were the hair and neck which were not touched by the morph. The midpoint of the shift wreaks of Photoshop-like effects (softening of the face alone). (00:41:50)
Deliberate mistake: So right before the containment team seal up the window with the tarp, the SWAT is shown having police dogs. The virus (which came from a dog in the first place) can be transferred through saliva. The SWAT obviously overlooked the fact that the potentially infected people who might escape could be bitten by the dogs.
Deliberate mistake: A stunt double for 47 got hurt on camera and yelled, very obviously. Right after the sword fight on the train the last man 47 is fighting continues the fight hand to hand under the tracks. Timothy Olyphants stunt double throws a punch and he grips his hand, yells and his face comes into screen for a moment. Next shot, Timothy Olyphant throwing his own punches.