Roku app outputs no audio for 5.1 tracks

Server Version#: 1.42.2.10156
Player Version#: 8.6 build 5

I just got the new Plex app update on my Roku TV, and since this update I get no audio output from any 5.1 content. No errors, just silence. Stereo content is fine in Plex, and other non-Plex 5.1 content on my TV works fine as well. The content in question (5.1 AAC) plays just fine in the Windows app, so it seems specific to the Roku app. I should also mention that it played just fine before the new UI update. Since there is no option to downmix to stereo, this makes the Plex app on my TV entirely useless. Has anyone else experienced this issue or know of any kind of workaround?