No Video with AAC/AC3 /w HEVC video



So like the video says, HEVC playback does not work on my iPhone 6s when AAC or AC3 is used as the audio codec.

In both cases, Plex is Direct Playing. If I set the iPhone to "Convert Automatically" then Plex converts the video to H.264/AAC and the video plays fine. This is also true for any media that is originally H.264 ACC/AC-3.

But if the video has MP3 audio, video playback works just fine.

No matter what I do, my 6s will not play HEVC files with AAC/AC-3.

Video working:
1920x1080, 59.94fps, 7.0mbps
MP3 2.0, 320kbps, 48000Hz

No Video:
1920x1080, 59.94fps, 4.6mbps
AAC 2.0, 448kbps, 48000Hz

1920x1080, 59.94fps, 7.8mbps
AC3 2.0, 448kbps, 48000Hz

The only difference that I can see is that the audio bitrate is higher on the nonworking files. Is there a limit for this in iOS and if so, should Plex be transcoding the audio?

And on that note, is there some way to force Plex to just transcode the audio? I guess I could just disallow Direct Streaming, but I'd rather not since I want content that does work to Direct Play without having to fiddle with the settings all the time.

Thanks for any help!

Edit: I just noticed that the MP3 version is Direct Streaming, not Playing. Any H.264 file does Direct Play. Not sure if the distinction is important.