Stupidity: At the beginning, young Indy knocks out the driver of the car, pulls him out, and just leaves him on the ground by the car while entering the car. Neither the knockout nor the unconscious driver lying around are noticed by any Germans in the vicinity. Not even by the soldier who opens the car door and the officer who gets into the car, both of whom immediately appear after Indy has gotten into the car. (00:06:00)
Stupidity: Despite being wanted by the law, quite possibly the most wanted man in the US for multiple murders, disrupting the most historic parade of the century, and with CIA agents on his tracks, Indy just gets on the commercial flight to Morocco the same evening without the slightest problem.
Stupidity: When Voller's van arrives at the airfield, the mechanic shot by Gunther acts as if some strangers have arrived, although in the airfield there is a big Nazi plane, Nazi soldiers, and all the people there work for Voller (as it's shown when plenty of men open the hangar's door). Strangely, the mechanic seems to never notice any of these things.
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 ★