Plex Client 5.1.1 (updated around Feb 7 or 8)

Plex Server: 1.11.2.4772 (also updated recently) running on QNAP NAS TS-453Pro

Roku Ultra: 8.0.1 build 4047-46

TV: Samsung LN32C540

Hooked up via HDMI

Files are MKV

No audio on AC3.5.1 files.

This issue popped up Feb 9 on some videos that have worked in the past. I am able to play the videos in the Roku Media Player from the Plex server. All indications point to the Plex client that just updated. I have:

rebooted the roku

factory reset and reinstall

Neither of these work. I don’t believe any changes were made to the settings on the Plex server and this issue isn’t happening on any other platform (just the Roku). I see a LOT of conversation about AC3 in the last few days and not sure what has happened. Any ideas? My Plex server is pretty much set up as standard but if you need info I can give it to you.