What happened? Very odd bug here. I have a UAD Apollo Audio interface. My mac audio is routed to Apolos virtual 1-2 Channels. You can see the Audio Midi settings in the uploaded image. Using Twitch there are some streams that play out of the wrong channels. For instance on one stream (https://www.twitch.tv/datto) the audio plays out of only the left side UAD Apollo Mon-L (the left channel of Apollos monitoring channel which is not virtual channel 1-2 my current Mac routing, but Monitor 1 only. Not even Monitor channel 2). On other stream (https://www.twitch.tv/aztecross) it works correctly. I've tested on other browser including ARC and there was no issue. I've ran the troubleshooting mode and the issue is still present. I even changed my UAD Apollos to the normal Mon L-R channels and the issue is still present. I'm wondering if Firefox has some issue with multichannel audio interfaces or audio interfaces in general? I attached 2 images of my UAD console. You can see in the first image that on the MAC Channel there is no audio coming through while watching the Datto twitch stream. But you can see on the L monitor (all the way to the right) there is audio. On the second image is a Aztecross twitch stream and audio is passing through the MAC channel correctly. Any idea what is happening here? '''Reproducible?''' I have checked that this issue is reproduced on Firefox, Firefox Nightly, Zen Browser. '''What platform are you seeing the problem on?''' macOS - aarch64