Trouble playing 4K content through the plex app

I’m having some issues playing 4K .265 files on my shield. Lots of audio cutting in and out and then stuttering/freezing. When I play the 4K file through Infuse on my Apple TV 4K, everything is fine. So it seems to be Shield issue? I’m also using a Samsung K950 for atmos pass through if that makes a difference. I have the most up to date plex app on my shield, and the following server version: 1.12.3.4973 (also most up to date)

I have direct play on and audio pass through set to auto in the plex app on the shield. Things were fine a month ago when I first got the Shield, not sure what broke it. Anyone else running into this issue?

Transcoding?

In Plex app set Display Information = On (Settings -> Video).

While playing video pull up on-screen display (pause, etc). App will show Direct Play / Direct Stream / Transcode in upper left corner. If one of latter two, it will display a reason if the audio or video is transcoded.

How are things connected? Shield to soundbar or to TV? Note that HDMI/ARC is bandwidth limited and does not support lossless audio such as TrueHD, dts-HD MA, etc, so could be an issue if Shield connected to TV.

What version of Plex app on Shield? https://app.plex.tv/desktop#!/settings/devices

Post XML for one of the problematic videos. See Investigate Media Information and Formats.