Isn’t this like an entire branch of historical science? Verifying transcriptions with secondary sources, seeking out potential translation errors, and estimating the confidence levels we have in various texts. Those are the primary job functions of historians.

It’s like asking “How do we know telescope lenses aren’t distorting images we see in them? Sometimes the images are even inverted so how much faith in those inages can we have?”

Like, no shit, that’s how telescopes work. Astronomers know how they work, and account for distortions, inversions, and like a million other confounding factors most people would never think of.