I've also been having this problem ever since Endwalker dropped. I've tried dx9, lowering bitrate, reinstalling the game, reinstalling my own drivers, setting low graphics, and lots of sound setting fiddling but I still get the sound stuttering. Dialog is timed pretty tightly so with the audio clipping on and off characters only get to say about half of their voicelines before moving on to the next line. Visually there are no problems, but I would really like to experience Endwalker in full, especially since the soundtrack is what drew me to the game in the first place.

Potentially relevant specs:

Motherboard: 990FXA Gaming MS-7893
Processor: AMD FX(tm)-6350 Six-Core Processor (6 CPUs), ~4.2GHz
Graphics Card: NVIDIA GeForce GTX 750 Ti

Let me know if further information would be useful in any way.