Montana Smith said:
All four movies are full of jarring moments - but I find that they only jar if you try to force real-world sensibilities onto the situations.
I disagree with your characterization. There is very little at all that is "jarring" in the first three films within the context that those movies create for themselves.
One could argue (convincingly, I'm sure) that there is very little that is less "realistic" in KOTCS than in the other films.
However, the movie is full of dissonant and phony moments throughout.
But take a look at the other films. The opening sequence in "Raiders", whilst filled with all kinds of obviously unrealistic moments, sets the stage for what follows. A universe is created and its rules are put in place.
The rest of the movie is consistent with the tone and parameters established in the beginning. Sure, there are plenty of "unrealistic" moments, but nothing that stretches the "credibility" of what has already been establish. It's consistent and it makes sense within the rules it creates.
We go along for the ride. Nothing really "takes us out of the movie" or stands out as being a particularly inconsistent, awkward or inappropriately "fake" moment. We have made a pact with the filmmakers to stretch our credibility to a very specific degree. We will suspend disbelief only so far - and the filmmakers never go back on their promise.
In fact, one of the things that made Indiana Jones such an endearing and memorable character off the bat was the degree to which the filmmakers gave at least the appearance of vulnerability to the guy. Indy has phobias. He is fallible, utterly failing in the opening sequence and consistently throughout the film. Indy shows pain, he gets knocked on his ass. He does incredibly, mind-blowing things, but later on has to recuperate and nurse his wounds.
All of these qualities serve as a very effective counter to the far-fetched events and stunts and actions of the story. We're grounded, in a sense, and, while few human beings could ever really do what Indy accomplishes, we find him a believable - even relatable - hero.
I would argue that the subsequent two sequels, particularly "last crusade", stretch the template that "Raiders" had established with increasingly fanciful happenings, which venture more towards the cartoonish. They are stretching our suspension more and more.
But it doesn't really break until the fourth movie. By that point, the filmmakers have left behind all pretense of making Indiana Jones a relatable, vulnerable hero in situations which we can believe in. Or at least not actively DISbelieve in.
There's a reason "Nuke the Fridge" entered the lexicon. At that point and from that point forward, the Indiana Jones team seems to have given up and gone back on those promises they made way back in 1981 with "Raiders."
One could argue that getting flung a mile or two in a metal fridge and surviving is no less plausible than jumping a massive gap in an out of control mine cart only to land perfectly on the tracks on the other end.
But the filmmakers make no concessions, as in earlier films, to ground Indy with flaws and vulnerability (though I think that trend really began in earnest in "Last Crusade", but fortunately there wasn't anything as outlandish in that movie to really break the spell.)
Story, plot and stunt elements in KOTCS are frequently (if not consistently) take the movie into "implausible" and cartoonish territories the other films did not dare to tread. And they abandoned any attempts to balance that by making the character himself believably human.