H264/AAC RTSP pushstream, H264 video dropped on outbound streams

Hello everyone, I am using ffmpeg-libav* to forward some webrtc A/V traffic from my gateway to evostream by pushing an RTSP stream into EMS port 5544. Forwarded A/V streams are H264/AAC. I am testing with online players. Something weird happens:

• it works fine if I open the player first and make it wait for the incoming stream on rtmp://<ems_ip_addr>/live/MyStream. As soon as I push my RTSP stream into EMS I see the A/V stream in my player.
• But it doesn’t work if I launch my player after having pushed my RTSP stream into EMS (so it doesn’t work if my inbound A/V is already feeding EMS when I launch my player)
• What happens in this last case is that only audio is forwarded by EMS. When I do a getStreamInfo on my outbound RTMP stream I see that video bytesCount variable is 0.

Video is not forwarded in the last case, and EMS doesn’t give any hint why video is dropped on my outbound stream. Do you have any clue why this doesn’t work in the last case where it works in the first case? What’s the difference from the RTMP outbound stream point of view between 1st and 2nd case? Thanks a lot, Emmanuel.