Revealing mistake: At the end the sides of the grave (which Jack just had dug by spade) are too perfect. Only an excavator could get such neat sides.
Revealing mistake: When the newscaster was filming Clinton giving a statement, the timer on the camera stayed at 0:00. The red "Rec" button, which supposedly was on, also looked fake. (00:10:35)
Revealing mistake: When James is getting on the St. Charles street car at Carondelet it's raining, but on the north side of Canal St, people are walking in shorts and with no umbrellas.
Revealing mistake: In the news reel detailing the Kohinoor theft, a few headlines appear, and at least one persists on screen long enough to easily spot the inconsistency between headline and article (filler text presenting a new local magazine from the London district of Lambeth). (00:09:00)
Revealing mistake: Crawling through a fire cave you can see propane bottles in the background several times.
Revealing mistake: When the stewardess asks April to sign her copy of the book entitled "How to Survive a Sharknado and Other Unnatural Disasters..." it's a thin book, and in the closeup as April autographs the page we can read the text and it's actually one of the versions of the "Samsung Galaxy Tab...For Dummies" book, not April's book. Also notice when Kelly Ripa shows April's book to the audience, it's now at least 4x as thick.
Revealing mistake: When Tom and Anna were jogging on a dirt path, the woman going in the opposite direction who passes them on the right would be walking straight into the kids (and woman) who were running past them on the left - but the woman on the right disappeared behind Tom's back where the collision would have occurred if she were really there. [Use of a green screen]. (00:29:25)
Revealing mistake: About seven minutes in, during the scene where we see Cooper helping the Nerd as a cameraman, you can tell that Cooper has been added to the scene using green-screen effects, as the actor was unavailable to shoot at the location. The lighting on Cooper doesn't quite match the lighting of the scene, and you can see a slight "blur/feathering effect" around him where the greenscreen background was removed.
Revealing mistake: When the camera pans across John's family sitting on a pew, there is a few to several inches between each body. The almost-still frame closeup view from John's end shows the bodies cramming/overlapping and the first four are blurring. (00:11:03)
Revealing mistake: Late on in the film; Arnie and the female officer kick in the door to one of his teams house. Unfortunately Arnie is in his 70s now and not as agile as he used to be, the door was open and simply pushed hard. Look at the door, it has no damage and neither does the frame. Also, the door barely opens past a hard push. As tactically trained operatives they would not have pushed the door if it was ajar either, they would have opened it slowly to avoid startling anyone inside and warning them.
Revealing mistake: Look behind the policeman when he shouts "Sir, get your hands away from the cables, right now." For absolutely no reason the extras (one in particular to the left that was looking in a different direction entirely) remembers to act scared only at the word "get", but the policeman already started shouting before, and sparks have been flying even earlier. (00:52:00)
Revealing mistake: It is obvious that the actor, Ellar Coltrane, is watching and waiting for the cue for "Mason" to start drinking from his can of beer at the pool hall. (02:03:44)
Revealing mistake: At the start, Doc shoots one of the watch towers that explodes. However, it explodes in a way that shows it to be made of something other than concrete. Something like card. (00:05:30)
Revealing mistake: In the beginning of the storm, a trashcan is blown down the street, by the wind. Most of the leaves, lying in the road, are not moving though. (01:28:05)