We just resently started having this same problem. We are distributing live video streams using RTMFP.
Dropping application (multicast/_definst_) message. Clients not allowed to broadcast message.
What does this message mean?
I've noticed that the stream will stop publishing from the server to the mulitcast group. This happens multiple times a day on all 11 of our live streams.
Also, I can fix the live multicast stream if I stop and restart the encoder.