The large X at the library is shown dark with a white background and a red frame when Indy is looking at it from the top of the staircase, but it has no white background when he starts breaking the tiles a few seconds later.
After swimming under petrol in the catacombs, Jones surfaces completely dry, except his wet hair, which makes wet spots on his clothes.
Indy and Elsa's boat is hit by submachine gun fire and sputters out, dark smoke billowing behind them. Elsa maneuvers the boat away whilst Indy duels on the other boat. When Indy is done fighting and his boat is being chopped to bits, Elsa maneuvers the boat back and ably picks up Indy and Kazim. That same boat (same bullet holes in the windscreen) is speeding down the Grand Canal a few moments later.
When Indy and his father are in the airplane while escaping the zeppelin, Henry shoots the plane's tail, ripping the top off. In subsequent shots of the plane, the tail can be seen with holes in it, but the top intact.
During the tank scene Indy is caught on the gun barrel by a strap, a situation from which he can't extricate himself. At the end of the fight however he is shown jumping back up onto the tank without untangling himself.
If a match would cause catacombs to explode, Indy's torch would have certainly set them alight first.
Blasting holes through the rudder of a small plane will not disable it, especially when Jones Sr.'s body was enough to cause wind drag. Although level turning would be impossible, the plane could still maneuver with the wing ailerons, which are more critical to level flight.
The entire sequence with Indy hanging from the splayed barrel of the tank is wrong. First, there is no way the strap on his satchel gets out and around the splaying for him to get caught. Second, when he realizes the strap is caught he acts like there's no way to get out. The strap is under his arm pit. It'd be easy enough to raise his arm and drop off. Third, after the tank abruptly swerves away saving Indy, in the next shot he's just jumping back up on the tank - satchel in place. How did he do that? He'd have to get the strap back out around the splayed barrel.
When Indiana and Henry Jones Sr. are attacked in the airplane they took from the zeppelin, and Henry accidentally shoots the tail of their own plane, he only damages the rudder and vertical tail fin. While this would impair turning, maneuverability, and directional stability to some degree, it would not affect propulsion, nor cause the plane to sputter and shudder and force an immediate crash landing, especially since they were flying relatively straight and level at the time.
When Father and Son have to escape the Blimp on an open air Biplane you'll notice during the close-ups of the dogfight between the planes both Jones not only have no problem keeping their hats on there's virtually no wind blowing their hair or anything else. This is clearly shot in a studio with a green screen, but it's glaringly obvious someone forgot to at the very least bring the fan to the shoot.
Some viewers have pointed out that Germans would never use a Rolls Royce for a staff car. They would have used a Mercedes-Benz or a Horch. However, this car was donated by an American traitor.
The tank used in the Nazis' expedition to the Holy Grail is a version of a World War I British Mark IV model, not a 1930s Panzer unit that would have been commonplace in the German army by then. That's because the tank was provided by the King of Hatay (who would be much more likely to have vintage British Tanks than Brand new German Panzers) rather than the Nazis.
In the library scene Indy discovers the "X" high up on the balcony. The X is green with a grey background. But when he breaks the tile to find the tomb the X has disappeared and the ground is a solid green. CORRECTION: This is a trick of the light, as the X can still be seen from ground level.
The band on grown up Indy's Fedora is wider than young Indy's. If it's the same fedora that was given to Indy in 1912, this would mean that he might have had the band replaced in the intervening 26 years. Alternately, it might not be the same hat, but one similar to the original, which may have been destroyed on one of his adventures.
Although the German Zeppelins could carry cargo (the Graf Zeppelin carried a car to South America), they were not equipped to carry and launch airplanes. Only the rigid dirigibles used by the US Navy could launch, retrieve, and house airplanes. However, the Indiana Jones films are largely intended as an homage to the movie serial segments of the 1930s-1940s, and some artistic license was clearly taken throughout the series for the sake of exciting action/adventure visuals and scenes. Additionally, some actual trapeze connection attempts on the Hindenburg were made in real life by World War I flying ace Ernst Udet, so this is not outside the realm of possibility.
During the tank fight there are several shots from behind the tank as it is moving. The tracks left in the dirt are from standard tires, not the steel tanks treads that they should be.
During the library scene where the large X is on the floor, Indy climbs a spiral stair case to get a better look at the floor. When he's at the top, the book case behind him is clearly made up of book spines glued to a black background.
Indiana and Elsa's clothes are wet, but are not stained or discolored by the oil.
When Henry Sr and Jr (Indiana) escape in the Zeppelin Plane, during the WHOLE flight (in close-up shots) there is no sign that they are flying, or even that high in the air. Nothing flaps, moves, flutters... notice that their hats are perfectly still. At that altitude, let alone flying an open cockpit plane at high speeds, there would have been a lot of wind. The shots were obviously done on a stage where someone forgot to turn on the wind fan.
When Indy is in the tomb under the library walking with the lit torch, flaming embers can be seen dripping off the torch into the "oil covered water". This would have ignited the oil just as the lighter did.
The grail knight's clothing is hundreds of years old but looks brand new. Nothing about the grail suggests it rejuvenates clothing.
When Indy and Henry Jones, Sr. sit down at their table on the airship, Henry's newspaper is upside down.
When Kazim is firing his MP28 sub-machine gun at Indy, it seems to break apart. The MP28 has a dis-assembly catch at the rear of the action, and the actor must have pressed this by accident, resulting in the barrel and action swinging away from the body of the
gun.
In the airport lounge, a person is reading a German newspaper dated 1918, twenty years out of date.
When Marcus Brody is captured by the Nazis and put in a truck, the truck gate that is closed behind him has the insignia of the Afrika Korps (a palm tree over a swastika). The action takes place in 1938. The Afrika Korps wasn't formed until 1941.
Indiana Jones goes to Berlin in 1938, according to the movie. There he sees the infamous "burning of the books." In fact, the burning of the books in the Bebelplatz by the Nazis took place in May 1933. Certainly, all the Nazi-condemned books would have been long ago confiscated and destroyed by 1938.
The car that the sheriff was driving to Indy's house in Utah back in 1912 is a 1914 Ford Model T.
The blue stamp on Indiana's father's envelope commemorates the 100th anniversary of Texas statehood: 1945.
The butler in the castle says "... and if you are a Scottish lord, then I am Mickey Mouse," but his mouth says "... then I am Jesse Owens". The line was altered in post-production because it was assumed that audiences wouldn't know who Jesse Owens was.
When Indy, his father and Sallah leave Iskenderun in the car to go after Marcus and the Nazi's, Dr. Jones in the back seat goes out of focus as he moves forward and then back.
The last Luftwaffe fighter plane gets disabled by the seagulls flying up, and we see the propeller stop and hear the engine sputter out. Yet in the shot of the plane whizzing toward its fiery demise on the hillside, we hear its engine droning again.
When the chubby Boy Scout is asking Young Indy what the grave robbers are doing, his lips are clearly not moving; the words were obviously dubbed in after the film footage was shot.
At the end of the boat scene, when Kazim says "Because you're looking for the holy grail." the voice does not match his mouth movements.
When Indiana finishes crossing the invisible path and enters the room with the grail and the knight you can just see the shadow of someone moving (its definitely not the knight's shadow and there wasn't a hat on the shadow either so it's not Indiana, either).
When Indiana Jones and the rest of the gang are escaping the crumbling tombs where the Grail was housed, you can see a man in a white tee shirt and jeans off to the right side just before Henry Jones looks back at the Knight.
You can see a member of the crew in the crack between the door and the doorframe in the background right before Indiana says, "How dare he?" and hits the butler.
When Indy and his father are escaping from the castle, right before the motorcycle chase, they set off an empty boat to distract the Nazis. Inside the boat there is a blanket and if you look closely you can see an arm that comes out from under the blanket and grabs the boat's rudder.
Before Indy's father frightens the seagulls into taking flight in the beach scene, the reflection of a camera is visible on his glasses during the close up on his face.
Unlike Rome, Italy, there are no catacombs beneath the city of Venice. If there were, they would certainly be below the water table and very likely flooded. Furthermore, there is no rock beneath Venice in which catacombs could exist. Venice is built on mud flats with hundreds of meters of poorly consolidated sands, silts, and clays below that. The foundations of the buildings are wooden pilings driven into the mud.
Signs written in English appear in German-speaking countries.
The beginning part of the movie is set and filmed in Moab, Utah. But when the Young Indy is being chased by men onto the train, they quickly go through some forested land for a long time, with a green meadow. The nearest landscape like that would be in Southwestern Colorado, or Central Utah, not Eastern Utah as depicted.
Young Indy is fighting on top of a railway truck which one minute is going past lush greenery then a rock cliff.
Indy notices the catacombs are flooded with petrol and proceeds to make a naked flame torch - this would ignite the fumes from the petrol and cause an explosion.
In the final sequence at the Grail Temple, in addition to the six "stars", there are also a detachment of about a dozen or so soldiers (both Hatay and German). When the "earthquake" hits, they are seen throwing down their guns and fleeing, but when the four "mains" (Indy, Dr. Jones, Marcus and Sallah) exit the Temple and mount their horses (standing peacefully in a group), no one else is ever seen anywhere as they ride off.
Though it is not stated in which months of 1938 the movie takes place, from the weather someone can guess it's late-spring. The State Of Hatay was formally established in September 1938 and joined the Republic Of Turkey in 1939. Moreover, during its short existence, it had never any royalty, since it was established as a republic.
Given that Henry Jones Sr. realized Elsa was working for the Nazis and the fact that he had time to mail his diary back home before he was captured he certainly had the time to include a written message to Indy not to trust her or bring the diary back to him.
There is no way that Donovan's men could have known that Indiana would exit the school through the window, only a few feet away, let alone at that exact moment.
In the catacombs after Indy passes the image of the ark of the covenant and approaches the next wall with the lighter, the shadow of a boom mic is briefly visible at the top of the lighted wall area.
In at least one scene, the SS officer Vogel is referred to as 'Herr Oberst' (Colonel), while his lapel insignia are those of a Standartenführer (SS equivalent to Colonel). An SS officer would have hated being called by an army rank.
When Vogel refers to Dr. Schneider, using the German word for "Miss" (which is Fräulein), he pronounces it "FRAW-line". A native speaker, however, would use the correct pronunciation: "FROY-line".
Indiana Jones in "Raiders of the Lost Ark" ultimately encounters all of the powers of the Ark of the Covenant. Yet when he becomes involved in the search for the Holy Grail he is dismissive of it as legend. Surely his experience with the Ark would have given him some sort of belief in the existence in a higher power and the stories associated with it.
When Colonel Vogel is in the desert with the party heading towards the site of the Grail (at 1h24m), he says "It must be within three or four miles, otherwise we'll be off the map". He's supposed to be a German, and in Germany, the metric system was the official system of weights and measures since the formation of the German Empire in 1872, and metrication efforts had begun in the German states, kingdoms, and principalities since after the Napoleonic Era in the early 1800s. He would have said "It must be within five to seven kilometres..." instead.
When Indiana Jones first sees the tablet, he identifies it as an Early Latin text from the mid 12th Century. The text is not Early Latin, but rather Late Latin. Early Latin refers to Latin before the Golden Age of Cicero and Caesar. In the 12th Century, people used only Medieval Latin.