Audio quality to ATV4 really bad on certain videos

Hi,
When I play certain files (one specific season of a TV show. MKV files.), the audio sounds absolutely horrible. Like, not just unwatchable but it also really hurts your ears. It's a weird echo-y repeating sound, like the audio is playing on top of itself 4 times with a bunch of static. Only happens on the Apple TV-- streaming these files to a computer works fine. I've had this a couple of times with other files, but it has gone away. With these files, it doesn't want to. Streaming from Mac Plex Server to, again, Apple TV 4. Already tried turning off direct stream and direct play, but plex has to convert these anyway since ATV doesn't play MKV files.
Any advice?
Thanks!
-Gabe