Messages sent from client right after DataChannel opened are lost at videobridge

[nojz]

Expected result:

1. Client A is connected to the videobridge, everything is established.
2. Client B connects to videobridge with DataChannel enabled.
3. Handshake is completed and DataChannel open callback is fired at Client B.
4. Client B sends message and videobridge accepts it and forwards it to Client A.
5. Client A gets the message.
6. Further messages are sent perfectly.

Actual result:

1. Client A is connected to the videobridge, everything is established.
2. Client B connects to videobridge with DataChannel enabled.
3. Handshake is completed and DataChannel open callback is fired at Client B.
4. Client B sends message but videobridge drops it so Client A does not receive the message.
5. Client B sends message after a few seconds and Client A receives it through videobridge.
6. Further messages are sent perfectly.

Why videobridge drops the "early" messages?
As far as I see the problem is around SctpConnection.java where the client handshake is completed on different thread than calling notifySctpConnectionReady which sets the callback for receiving messages.
So the handshake completes earlier and on the other thread the callback is set too late. If the client sends message between these then that message is dropped/lost.

Right now we use a sleep workaround but of course it's inefficient, ugly and in theory could be unreliable.
Could you take a look at this problem please?