Specifically, if one of the 206 requests for audio fails and buffering stops, is there a way to detect that state? Or should I have to check if buffering stopped by comparin
There is a complete list of the events handled by media elements in the spec: https://html.spec.whatwg.org/multipage/embedded-content.html#media-elements
I would look specifically at the stalled, abort, progress events.
Since this element is relatively new implementations may vary greatly. So I would test these events against the platforms you are targeting to see if they work as expected for your needs. If not you may need to do something a bit more manual like polling the buffered state as you had mentioned.