Revealing mistake: During the scene with Maverick and Rooster in the F-14A, you can see the cockpit of the F-18F being reflected off Rooster's visor on the helmet.
Revealing mistake: There's something odd about the chair that is (or is not?) to the right of Monsignor Kelly when Stu goes into his office to talk. Only part of the back of the chair can be seen and it is not directly in front of the Monsignor, but there is not enough room for the seat part to be there (otherwise, the Monsignor could not be standing where he is). Without any indication that the Monsignor or chair moved, the Monsignor is later able to rest his right hand on the chair's back. (01:13:57 - 01:14:37)
Revealing mistake: The front and rear views of the house did not seem to properly fit together. The rear view showed more sections, making the house longer than what the front indicated and had three high chimneys compared to only one from the front. The rear view also showed several trees that would be aligned in front of the house, but the trees did not appear to be situated that way. (00:27:49 - 00:29:52)
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: 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: During the battle of the Chosin Reservoir, just before VF-32 comes in to provide air support, the Marines are firing their M1 Rifles. One of them mimics the recoil of it but we don't see the bolt move back when he fires his rifle. The M1 Rifle or Garand is semiautomatic, and the bolt moves back each time the shooter pulls the trigger.
Revealing mistake: When Otto, Tommy and Marisol find the frozen cat outside of the house it is a puppet prop. A few seconds later Tommy is holding it now back to a real animal and is bone dry.
Revealing mistake: Younger Tom dropped his policeman's jacket onto the "fire" and when Younger Marion came over to the fire (almost 30 seconds later), the jacket still had not caught on fire. The next time the jacket was shown, most of it still looked unscathed by the fire. (01:33:30 - 01:35:36)
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: There are noticeable differences in the appearance/condition of the lattice panels on the deck (overlapping; whether there are missing/broken slats and, if so, their locations), but pinpointing most of the differences would require pausing. When Thomas was seated in front of the panel adjacent to the door, sometimes there were broken/missing slats but other times they were intact. Most revealing was the absence of the lattice panel opposite the front door when Liz was standing near Thomas. (00:42:17 - 00:49:42)
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: Luke points a flashlight along the side of the staircase, but no shadows are produced on the wall from the vertical posts. Luke points the flashlight in front of himself and produces his shadow on the wall behind (and the shadow doesn't look like the way he is holding the flashlight). After Luke goes through the entryway aiming his flashlight ahead, a circle of light is behind him. The power is out, so the flashlight is the only light source - except that used for filming in the dark. (01:03:00 - 01:05:25)
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: 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: 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)