[SPOILER] 'Father and Son' - Polybius square puzzle

[Einstine]

In an effort to better try and understand the puzzles, I wanted to ask what clue I was missing with this one. The last letter was where I was stuck. I had it as an 'A' while the puzzle uses it as an 'O'. How was I supposed to determine that was an 'O'? This just seems like one I would have never solved but for random guessing.

Just wondering if I should plan on puzzles with random guessing or if I need to look deeper into the info given.

Spoiler - Pic of poem with letters circled
https://imgur.com/a/LknexgM

[Arathir]

If you look at the difference between the two things (the one you though it is and the one it actually is) elsewhere in the poem, it is clear that it is supposed to be the latter, so no random guessing required. In other words, it does look like the other O's in the text instead of A's, but the difference is quite small. The body of the letter is slightly more narrow and the connecting line is a bit higher in the O than in the A

That being said, I analysed it the same way you did at first and only after the solution did not work I had another look at it.

Edit: You can see the difference between the first two words (PredicO lA) or the end letters at first and second line.

[Einstine]

I think I got hung up, in the back of my head, on how I was taught cursive, and the 'O' is definitely not it. Specifically, in how I was taught, the connecting lines for an 'O' both connect near the top of the letter, while the 'A' is the one that drops down each side some before disconnecting.

All that said, it's a puzzle so I guess they had to create another level of challenge, by obscuring, rather then simply 'connecting the dots'.

It did free my thinking up some as now I approach puzzles knowing there may be a bit more 'jank' than I would expect, so I need to guess and randomize more.