Factual error: When Indy is wearing the uniform of a German Artillery Officer, he is wearing the ribbon of the 1939 Iron Cross 2nd class in his buttonhole. The movie takes place in 1938. (01:09:05)
Continuity mistake: When Old Dr. Jones is holding Young Dr. Jones while he is reaching for the grail, watch Indy's left hand. In the shot from above, it is by his side, in the shot from below, he is holding the rock. It keeps switching from his side to the rock.
Factual error: The evil SS officer is addressed as "Herr Oberst" (Colonel) throughout the movie. In the SS, however, this rank was called "Standartenfuehrer". (00:56:40)
Suggested correction: In fact, Oberst is the literal translation of the word "Colonel" into German. It would not be unusual for Germans to call a colonel by his rank in his native language (even if he is an SS colonel).
This correction doesn't address the mistake, which is the rank on his uniform isn't what he's addressed as. It has nothing to do with what the word translates into (which the mistake even points out).
Continuity mistake: When the Nazi is strangling Indy with the chain, Indy looks down into the porthole of the tank and yells, "Dad!" Before he throws the gun down into the tank Indy's hat comes loose, but when the next shot is back on Indy, and he yells, "Dad! Dad, get out!" now his hat is back to normal.
Visible crew/equipment: After Elsa gives Donavan the false Grail, he turns and you can see the reflection of the camera lens in the cup. (01:51:45)
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Continuity mistake: When we first see the knight guarding the Grail, his cloak is tied off with a braided rope, which hangs down on his right side. It stays this way until he says "You have chosen wisely," where the rope has somehow shifted to his left side. The rope goes back to normal when the knight waves goodbye at the end of the movie. (01:49:10 - 01:54:05)
Continuity mistake: After Sr. says "Let it go" as Indy is trying to get the grail, Indy is swinging and not being supported by the wall. The next camera angle shows him grasping the wall near his head. Switched back to Sr.'s view, he is again not holding the wall.
Continuity mistake: When the white robed men ambush the Nazis just after they blow up Salah's car, there's a shot over a Nazi's shoulder as he fires at one of the white robed guys running up a hill. The Nazi's machine gun is held straight out and doesn't move but the dust that flies from the squibs suggest that he fired as he moved the gun right to left which he did not do. The odd thing is that AFTER the squibs go off, the Nazi turns his gun to the left. (01:25:55)
Factual error: Indiana Jones checks his dad's grail diary to find the picture of the stained glass window in the church in Venice. With the book open to that page, the picture is on the left-side page, and under Indy's thumb on the right-side page is a snippet of an article about marriage statistics. The article mentions statistics up to and including the year 1943. Problem is, the movie takes place in 1938. (00:27:00)
Other mistake: In the catacombs, Indy flips over the casket with the skeleton and dives underneath together with Elsa. If you watch closely, the skeleton gets trapped inside the casket, however Indy and Elsa are alone inside the casket. If the skeleton had sunken, there wasn't enough time, nor did Elsa or Indy bump into it when they dove underneath.
Revealing mistake: After Indy jumps onto the tank from the horse there's a shot where he stands up to face the bad guy if you look at the tracks on the sand behind him, they aren't caterpillar tracks but tyre tracks. The reason is that for the close-up shots a fake tank was built on top of a car, a security measure to avoid anyone getting hurt in case they fell off.
Factual error: When Hitler signs the Grail Diary, in the screen and VHS release he signs Adolph, not Adolf. This mistake was corrected in the DVD release. (01:07:35)
Factual error: When Indy and his Dad are in Berlin, there is a big book burning going on. But the only book burning that was held in Berlin was May 10th in 1933 - 5 years before the Joneses visit it in search for the Holy Grail. (01:07:50)
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Continuity mistake: When Indiana is drinking champagne with the businessman in the fancy apartment he holds his glass by the stem in one shot and then by the bowl in the next shot. As the conversation continues the glass goes up and down in Indiana's hand like a yo-yo.
Continuity mistake: When Marcus is taken to the temple by the Germans, the knot on his tie differs between a far shot and a close one.
Continuity mistake: On the tank a soldier jumps from Indy's right to attack him. The following angle shows the soldier coming from the front.
Continuity mistake: When Indy and Elsa are wading in the petroleum looking for the knight's tomb, Elsa unbuttons and opens her jacket and starts to take it off. In the next shot she opens her jacket and takes it off again. (00:34:15)
Other mistake: On the zeppelin, Indy's dad says, "You left just when you were becoming interesting..." Harrison Ford is mouthing Sean Connery's lines. (01:14:50)
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Continuity mistake: In the beginning where Indy is young, he fights some guys on that zoo train. When he's on the crate with the rhino in it, the background changes in each shot. Once there are trees behind and a split of a second later there are rocks, once there's a cliff and once a plain, and it all changes in splits of seconds as they change shots. (00:07:25)
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Continuity mistake: When the Nazi Colonel discovers Henry Jones sen. aboard the zeppelin, Indy asks him for his flight ticket. In the first shot, Indy is standing right beside the colonel (the camera is behind the colonel and Indy comes in from the right), in the subsequent shot, Indy is standing behind the colonel.