Only use_media_proxy once
If you ever see strange sdp content like the following:
...
c=IN IP4 68.142.145.14568.142.145.145
...
m=audio 3501835018 RTP/AVP 0 8 3 98 97 101
...
That is, the IP address and port are repeated back to back (which really throws
off the far end), and you are using openser and mediaproxy, then you are
probably calling use_media_proxy twice in your ser routing. Apparently, this
is a bad idea.