Revealing mistake: When the boulder rolling down the hill hit the man, he "vanished" - he was not flung into the air and it did not look like he got run over by the boulder. [Poor/ineffective CGI]. (00:31:55)
Revealing mistake: When William and Jack open the door, enter the room, and walk past the helium-filled balloons (tied to a chair about 4' away), the balloons remain immobile. Due to how light helium balloons are, just opening the door or breathing nearby would be enough to cause the balloons to move somewhat - if they were actually there. (00:16:00)
Revealing mistake: Obvious use of a "green screen" when Elvis and Dylan are sitting on the steps in the stairwell. The five distinct steps that could be seen behind them become a gray wall and the blue handrail posts to the right of the screen become oddly grouped, appearing to be parallel to the right side of Elvis' shoulder/back. (01:09:00 - 01:09:25)
Revealing mistake: When Danny and the others are riding in the "RLC" truck to the bank, the sky is mostly a pale blue (almost white at times), but is suddenly a darker blue between two buildings. After returning to mostly pale blue, the sky turns into a much larger area that is a darker blue, then goes back to pale blue. Suggests filming on different days and/or use of CGI to fill in the sky but failing to use a consistent or similar color. (00:18:25 - 00:18:56)
Revealing mistake: This happens in the second ceremony when Wolf didn't press the button to shut off the lights to steal the golden dolphin because of the good comments. Few seconds later, the lights shut off, and you can see that the meteor on the top disappears at the time.
Revealing mistake: The boat's motor/engine was in the center-rear when Annie and Jodie brought it to the beach, but when Nic and the others were looking at the boat, the motor was off to the side (near the corner). The position of the motor varied, sometimes being in the corner when one of the riders would have obstructed its view. The appearance of the motor and which direction it was facing, the size of the tiller handle, and whether the water inlet port/propeller could be seen also varied. (00:48:57 - 00:49:47)
Revealing mistake: In the scene wherein Detective Marquez and Senora Borden are drinking wine by the (indoor) pool, the back of Det. Marquez's head is disproportionately large. Front views of Det. Marquez often show his head tilted to the left, but rear views usually do not and his head might even be tilted to the right. Also, Senora Borden's eyes do not appear to be aimed correctly at Det. Marquez's (especially since they are facing each other with heads tilted to the right). Use of stand-in and/or green screen. (01:02:30 - 01:03:10)
Revealing mistake: The $100 bills in the briefcase looked quite fake and were obviously a prop. (00:13:40)
Revealing mistake: When Chris Evans is dragging the girl into the maze at the end you can see the burn mark on his shoulder creasing with his shirt.
Revealing mistake: Dave Bautista announces that he has arrived. There's a close-up of the kickstand, and you can actually see scratches on the asphalt from previous takes (spotted also by Rian Johnson himself in his video breakdown of the arrival scene for the Vanity Fair youtube channel). (00:15:10)
Revealing mistake: The chalet was visible behind Emily when she was outside talking on the phone, but subsequent views of Emily showed her in front of a solid white background (mimicking snow) - indicating the use of a green (white?) screen. (00:13:34 - 00:13:56)
Revealing mistake: The "rain" moves with Nina, being heavier (or present) on which side of the screen she is on. Then there is no rain on the street when Nina is off-screen, but it is pouring behind her when she gets inside the building. (00:14:35)
Revealing mistake: The French tanks that attack Paul et al. Towards the end of the second act are supposed to be Saint Chamond tanks. There is only one of those left in the world, and it is not on screen: the undercarriage and tracks don't even come close to looking like that of a Saint Chamond, because it's actually a BMP-1 dressed up to look like a Saint Chamond.
Revealing mistake: The cell bars appear to be about 4" apart, but are much wider to accommodate the width of The Artist's face/head when there's a close-up of him next to the bars. (01:13:50 - 01:15:09)
Revealing mistake: Driving home from meeting Gigi, there is an image on the windshield of a blue handicapped parking permit/placard that is supposed to be hung on the rearview mirror, but there is no placard hanging - the permit's image is superimposed on the windshield. The image even briefly appears and reappears. (00:34:05)
Revealing mistake: Corporal Shah is tied and on a chair in the command center. He then receives a powerful blow to his left check, knocking him sideways and rendering him unconscious. But his glasses do not even move a millimeter.
Revealing mistake: The aerial view showed it was not raining during the "supercar race", but the ground views showed at least two cars getting sprinkled on (one enough to turn on the wipers). When the camera shifted to road-level, the cars and road were dry. (Suggests filming at different times). (00:31:15 - 00:31:48)
Revealing mistake: The appearance of the buildings/scenery opposite of FBI Director Gabriel Robinson's office vary, indicating the occasional use of a "green screen." The angles are inconsistent (wider or in the opposite direction) and sometimes grass and/or trees can be seen where the avenue between the buildings should be visible. (00:10:05 - 00:10:38)
Revealing mistake: The size of the spider walking off Sam's face becomes disproportionately smaller too fast compared to its size while on her cheek plus the spider's awkward movements are indicative of CGI. (00:02:20)
Revealing mistake: The owl that JP saw was obviously "fake" (stuffed or CGI). Its nose was crooked and its puffy cheeks made it look like it had cheek filler injections; owls have flat faces. (00:32:50)