Factual error: Skara Brae is on Mainland Orkney not the West Coast of Scotland as Indy states in class just before he's let go from the university.
Visible crew/equipment: Indy is at the nuclear test site and exits the house and comes out front. He knocks over the boy on the bike and air raid siren goes off. Just as he stands upright, in the window with curtains, you can see a reflection of a crew member walking by.
Continuity mistake: A car ploughs through huge iron gates, ripping them from the their hinges. Seconds later the car is pristine.
Continuity mistake: When Indy and Mutt are seated in the diner, Mutt stands up fast in an argument between the two, causing the bottles of ketchup and mustered to be knocked over. The shot then alternates from different directions, making the bottles appear as both standing and knocked over. When Mutt finally sits back down Indy sets the bottles back upright.
Revealing mistake: When the baddies are chasing Mutt's bike, right after they exit the cafe they skid to the left. Skid marks from previous takes are visible on the road.
Continuity mistake: After the monkey chase scene, after Spalko's jeep lands on top of Indy's, Indy, Mutt, Mac and Oxley start to raise, but when the angle changes they're crouched again, plus in a completely different position.
Continuity mistake: Oxley takes the skull out of the bag and places it behind his hand to scare the ants away. When the angle changes there's a brief glance of his right hand and the bag is gone.
Revealing mistake: At the end Indy picks up a heavy slab and uses it to knock the carved faces off the wall. He hands it to his friend Mac, then takes it back off him - at this point it's clearly a very light prop.
Continuity mistake: In the wedding scene the bride has open toed shoes when she kisses Indy and begins to exit the pulpit area, but different closed toe shoes as she and Indy depart the church.
Continuity mistake: By the waterfall Indy says "Nobody else can" and then Mutt's wet hair swaps from brushed backwards to messy.
Continuity mistake: During the quicksand scene, when Mutt is throwing a snake at Indy, Indy's left (our right) sleeve swaps from covered in sand to spotless between shots.
Continuity mistake: When Mutt and Indy enter the library, a chubby man in a suit holding a brown briefcase runs away, yet appears calmly walking half a second later from a different angle.
Continuity mistake: Mutt's bike passes by a group of strikers in the campus, and heads for the red banner. When the angle changes, a second group of strikers has suddenly appeared out of nowhere next to the banner.
Revealing mistake: When Indy and Mutt ride on the bike in the college gardens, there's a wide aerial angle that reveals that the distance to the red banner is very short, yet in every following angle they're repeating the same route over and over again (3 times at least) to make it look way longer and increase the suspense.
Continuity mistake: When Indy is about to hop on Mutt's bike, a man walks behind him twice. First time slowly, second time fast.
Continuity mistake: At the Mexican market, while Mtt is playing with his pocket knife, watch the chrome part of the light: it reflects a barren place with a brown squared building. When the angle changes it all changes to a bus and a lot of people hanging around.
Continuity mistake: Inside the waterfall, Ox takes out the skull, moves his hand from the top to the side of the skull. The angle changes and the hand remains on the side, but when the angle changes to behind Ox his hand is on top of the skull, repeating the first movements.
Continuity mistake: Inside the waterfall Ox takes out the skull while Marion watches from behind. When the angle changes, her hand is suddenly on his shoulder.
Continuity mistake: Indy uses a huge rock to smash the stone where sand is coming out and hands the rock to Mac. From one shot, Mac falls backwards and sits down, but from a different angle he is standing up slightly crouched.
Continuity mistake: Ox takes out the skull, Marion walks behind him, moving to a corner on the right. In the next angle Indy says, "Ox, I think I understand" and Marion is suddenly gone, only to magically reappear a frame later.
Suggested correction: I'm watching the Disney+ copy frame by frame, and there's no reflection anywhere.
Sacha ★
Actually, the mistake is correct. The crew member's reflection is at 00:19:32, reflected on the right curtain over Indy's right shoulder, next to the fake boy inside the house.
Big Game