This issue is related to playing media in Firefox. While trying to stream audio after moving workstations, I get the following error in the console:
Media resource [...] could not be decoded [...] NS_ERROR_DOM_MEDIA_MEDIASINK_ERR (0x806e000b) Details: OnMediaSinkAudioError
In this case, it's not down to the website setup or contents of the audio stream, as they were working before.
Searching online for OnMediaSinkAudioError or NS_ERROR_DOM_MEDIA_MEDIASINK_ERR only seem to turn up with code commits or repositories for Firefox itself, so this doesn't appear to be a common problem.
It turns out that in this scenario, the error is quite misleading, since it is caused by a misconfiguration of the Windows audio output device.
After swapping my headphones from the rear audio ports to the front and restarting the workstation, everything worked fine. Restarting Firefox may have also been sufficient.