Prior to enabling mod_av - SDP as below 
Local SDP:
v=0
o=FreeSWITCH 1527953490 1527953491 IN IP4 10.113.8.213
s=FreeSWITCH
c=IN IP4 10.113.8.213
t=0 0
m=audio 20064 RTP/AVP 102 9 0 8 103 101
a=rtpmap:102 opus/48000/2
a=fmtp:102 useinbandfec=1; maxaveragebitrate=30000; maxplaybackrate=48000; ptime=20; minptime=10; maxptime=40; stereo=1
a=rtpmap:9 G722/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:103 telephone-event/48000
a=fmtp:103 0-16
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20
a=sendrecv
m=video 29292 RTP/AVP 96 98
b=AS:10240
a=rtpmap:96 VP8/90000
a=rtpmap:98 VP9/90000
a=rtcp-fb:96 ccm fir
a=rtcp-fb:96 ccm tmmbr
a=rtcp-fb:96 nack
a=rtcp-fb:96 nack pli
a=rtcp-fb:98 ccm fir
a=rtcp-fb:98 ccm tmmbr
a=rtcp-fb:98 nack
a=rtcp-fb:98 nack pli



after enabling mod_av - SDP becomes 

failing invite 
Local SDP:
v=0
o=FreeSWITCH 1527945801 1527945802 IN IP4 10.113.8.213
s=FreeSWITCH
c=IN IP4 10.113.8.213
t=0 0
m=audio 27414 RTP/AVP 102 9 0 8 103 101
a=rtpmap:102 opus/48000/2
a=fmtp:102 useinbandfec=1; maxaveragebitrate=30000; maxplaybackrate=48000; ptime=20; minptime=10; maxptime=40; stereo=1
a=rtpmap:9 G722/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:103 telephone-event/48000
a=fmtp:103 0-16
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20
a=sendrecv
m=video 32616 RTP/AVP 96 98 100 102 127 125
b=AS:10240
a=rtpmap:96 VP8/90000
a=rtpmap:98 VP9/90000
a=rtpmap:100 H264/90000
a=fmtp:100 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f
a=rtpmap:102 H264/90000
a=fmtp:102 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f
a=rtpmap:127 H264/90000
a=fmtp:127 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=4d0032
a=rtpmap:125 H264/90000
a=fmtp:125 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=640032
a=rtcp-fb:96 ccm fir
a=rtcp-fb:96 ccm tmmbr
a=rtcp-fb:96 nack
a=rtcp-fb:96 nack pli
a=rtcp-fb:98 ccm fir
a=rtcp-fb:98 ccm tmmbr
a=rtcp-fb:98 nack
a=rtcp-fb:98 nack pli
a=rtcp-fb:100 ccm fir
a=rtcp-fb:100 ccm tmmbr
a=rtcp-fb:100 nack
a=rtcp-fb:100 nack pli
a=rtcp-fb:102 ccm fir
a=rtcp-fb:102 ccm tmmbr
a=rtcp-fb:102 nack
a=rtcp-fb:102 nack pli
a=rtcp-fb:127 ccm fir
a=rtcp-fb:127 ccm tmmbr
a=rtcp-fb:127 nack
a=rtcp-fb:127 nack pli
a=rtcp-fb:125 ccm fir
a=rtcp-fb:125 ccm tmmbr
a=rtcp-fb:125 nack
a=rtcp-fb:125 nack pli

The inclusion of H.264 then appears despite not being included in the codec definition in vars.xml