Revealing mistake: During the castle scene, when Indy is swinging outside, the sky is clear and blue and obviously not rainy, yet it is still raining. And yes, sometimes it can rain when it's sunny, but take a look - it is NOT rainy weather.
Revealing mistake: After the Nazi tank drives off of the cliff and hits the bottom, the upper turret breaks off. As the turret rolls over, you can see there is no hole in the bottom, just in the top.
Revealing mistake: When Indy is clinging to the side of the tank turret in the desert, to the right of the tank are tire tracks from the vehicle shooting the scene. They appear to just start at a set point. There was likely no way to hide this.
Suggested correction: There's no obvious moment in the film where tire tracks are visible while he's clinging to the side. A specific time or shot description is needed.
Revealing mistake: When Henry says "Faster, boy, faster!" to Indy when they are driving into the tunnel to escape the flaming aircraft, you can see the track that the flaming aircraft is sliding on.
Revealing mistake: When Indy shoots three Nazi soldiers with a single bullet during the tank chase sequence, you can see the blood packets inside their uniforms.
Revealing mistake: The stuntman who saves Indy's dad from the tank has a perfectly trimmed beard and a thinner face than Sallah's.
Revealing mistake: When Indy and Kazim are fighting on the front of the boat, the front of the boat doesn't move at all when the huge propeller hits the rear of the boat.
Revealing mistake: When Elsa falls through the crack in the hole, she is swallowed by a big cloud of smoke in the void. However, her silhouette is visible underneath the smoke, revealing she never falls any deeper, and thus giving away how shallow the hole was.
Revealing mistake: When the VW gets stuck on the front of the tank and is shot off, you can see that the car has no engine, no body in the car, and no clutch. Also, when the car is blown away you can see a wire used for the stunt fall right in front of the camera.
Revealing mistake: When the car is chased by a plane and enters a cave, check the rocks above the entrance and you'll notice that both the entrance and exit are the same location and the final shot has been flipped.
Revealing mistake: In the temple, when Indy walks on air, he briefly becomes semi-invisible due to the matte effect.
Revealing mistake: The seagulls on the beach (when Dr. Jones scares them with his umbrella) are blatantly fake. They don't move an inch. This was also confirmed by producer Robert Watts in this making-of video https://www.youtube.com/watch?v=BMFMKsrXuGY (minute 2'30").
Revealing mistake: When Marcus Brody is knocked out in the library, he is dragged away by two of the assailants. You can see the unconscious Brody give his right hand to the assailant.
Revealing mistake: When Walter Donovan is dying after drinking from the wrong cup, watch the over-the-shoulder shot where we see his hair grow long suddenly - for some reason, this shot was filmed in reverse, as the fire coming from the candles/torches behind Elsa is not burning upwards, but appears to be "sucking" back downwards.
Revealing mistake: In the shot of Elsa falling to her death into the misty chasm in the Temple, you can see that it is not Alison Doody but a stunt double.
Revealing mistake: When the tank shoots-up the jeep the interior is revealed to be empty and such a prop.
Revealing mistake: Dr. Jones fires at the jeep from the tank, but the explosion doesn't come out the cannon, nor by the jeep's window next to it; instead the back of the jeep explodes.
