When Nathan finds the case of Zippo classic wind proof lighters in the train museum shop, he immediately tests it out and strikes a flame. This is not possible as Zippo lighters are shipped without fuel, one must add fuel after purchasing the lighter.
When everyone is celebrating their victory in the final scene, some actors have no implants and others do. However, with the destruction of the robots, the electronic implants are non functioning. One of the extras in the celebration victory at the end (at around 1h 21 mins), forgot to turn off his implant battery and it can be seen briefly flashing.
Just after Kate (Gillian Anderson) is seen riding the horse on the beach, the kids on their obtained vehicles can be seen catching her up on the road in the background. Initially, the Jeep is ahead of the quad bikes, but after the jump cut, the quads are in front.
When Nathan is electrocuted in the first part of the film and his implant is switched off. It is behind his right ear. Though when the group venture out and he stops to complain about carrying the battery it has moved to behind his left ear.
Before reaching the Silver Mine, there are as many scenes in which you can see Sean wearing the implant as there are of him not wearing it.
The vast majority of the outside locations filmed show evidence of a thriving civil service (clean streets, bins emptied, infrastructure maintained). If no-one is allowed outside, why are the streetlights still turned on at night?
When Smythe (Ben Kingsley) is shot and falls over a wall an onto a pile of tarps/garbage, a safety cable is briefly seen immediately when the POV changes from the fall to him getting up.