Working on a simple JavaScript SIP client myself, I encountered the issue again. The browser sends:
a=group:BUNDLE 0 1
a=mid:0
a=mid:1
Asterisk returns:
a=group:BUNDLE audio-0 video-1
a=mid:audio-0
a=mid:video-1
Where it should return something similar as the browser instead, resulting in the exception:
Failed to set remote answer sdp: The order of m-lines in answer doesn’t match order in offer. Rejecting answer.
Adding Content-Type: application/sdp to the INVITE solved it for me.