Revealing mistake: Throughout the dive boat interior scene - after they dive on the wreck - various hanging items are swinging around randomly to give the impression the boat is rocking on the water. However, none of the key light shadows - from the exterior sunlight - move at all, indicating the boat is entirely static in a studio.
Revealing mistake: During the flashback scene, when young Indy jumps on top of the train and runs on the roof of the carriages, it's a very obvious and lame animation with unrealistic movements.
Revealing mistake: When the AA machinegun on the train goes berserk and destroys everything, Indy hides behind some crates. For several shots, Harrison Ford is replaced by a lame CGI, which transforms his head into a videogamish, lifeless face.
Revealing mistake: When young Indy jumps from his car to the motorbike and fights against a German - and the following scene where he rides on the bike towards the train - his body and especially his face are a blatant CGI creation with unnatural movements, dead eyes, and waxy, lifeless expressions (most noticeable in theater screenings). (00:05:53)
Answer: There is a bit of dialogue en route to the airport when Voller sets the instrument that says, "the first hand sets the destination," as in the time you want to travel back to. This would make the device completely absurd in principle if true (that's why I wanted to mark it as a plot hole/stupidity). Since it's supposed not to open portals but just detect them, it can't be that there are infinite portals for every moment in time you can choose to go back to (and they even close). The sky, while vast, is not infinite. We then find out that it is a trick since it is set to actually bring you to just one destination, but they don't know it yet.
Sammo ★