What does “that webrtc stream doesn’t include audio” mean? To provide some information on how it works - there are multiple streams, all bundled together over the same ICE IP/port.
Ultimately for something like this it requires a deep dive on both the browser and likely Asterisk. I will say I’ve also encountered weird behavior in the browser in the past adding/removing/changing streams within the browser itself, and have talked to others who experienced the same.