Duplicate sctp message

Hello.
I have strange behavior with sctp.
I have a sctp client that send 10 sctp messages to an echo server that returns them back. Each message is in a separate stream from 0 to 9 and each message has 0 ssn(stream sequence number).
All is good if both server and client are on a localhost. But if the server is on an other physical host then sometimes client can read same echo message with same ssn twice.
Client receives all messages back but i need to call sctp_recvmsg more times because of that.
tcpdump shows that hosts send all messages only once but in case of this duplication their order is a little different.
For some reason It only happens with first message.
What is going on here?