Although I think it’s likely that Sanborn made errors while cutting nearly 2,000 characters; we cannot rule out the fact that they were intentional especially due to his quote about their positioning being important.
I tried to isolate a few but they are L, O, E, E out of the K1-3. Maybe if we include the typos from the morse code, that will yield something?
I’m counting as a typo anything misspelled or left out.
Morse code: I, ON, and Possibly and I from “(I)t is your position”
Copperplate: L, O, E, E
It wouldn’t appear there are enough letters to form an answer that really stands out. Given Sanborn’s quotes on the positioning being important it’s entirely possible they bear some relevance to the final solution. I would say that my efforts to find a clue in the typos is at an end until K4 is solved. Perhaps then we will have an extra letter or two and something useful can be obtained. By anagramming the letters you can get some tantalizing phrases though…
“No one lie” (missing an n)
“Noon lie” (with a left over e)
“I alone know” (need a k, a, n, w)
“Noel ioe” (?)
“No love” (need a v, and have a left over ie)