If the text is longer than three lines, whatever the last line is will experience the same problem as seen with just one line of dialogue. Pressing A in that instance brings up the entire text box for reading. This also happens when the text box is 2-3 lines of dialogue long, and if you wait long enough you can see it trying to fill in the dialogue. Pressing A just moves to the next text box. For example, if the text box said 'Good Morning', all I see is 'G'. Simply put, if vsync is on I am only able to see the first letter/punctuation of whatever the NPC is saying.
The solutions/patches suggested were also years old. I've seen other posts about text glitches, but none that matched what I'm experiencing. However, activating it causes a text glitch in the game. The only thing that has worked so far for me is activating vsync. I've been playing around with the graphics to fix some lag issues I'm experiencing in the populated open world areas (places indoors, mines, or inside/outside my home are fine).