Try to set
webrtc_cc_min_bitrate=1000000
And do wcs restart
service webcallserver restart
Please attach your webrtc-internals graphs after this test.
You can also test VP8, it has better bitarte
codecs=opus,alaw,ulaw,g729,speex16,g722,mpeg4-generic,telephone-event,vp8,h264,flv,mpv