I was typing in notes and got the repeated text after I dismiss the keyboard to see what I typed, but when I started to type again my original text was replaced by what I was typing now.
I replicated this by dismissing the keyboard, touching a line of text, and then going back to type some more. Whatever I have touched and put the focus on gets replaced. Note: I am not doing a double tap, just a single tap to read that sentence.
I hope I have made myself clear.