I’m assuming here that the source stream is an RTMP stream, and that the stream is a high-bitrate stream. If these assumptions are wrong, please let me know.
On the EMS, you can increase the maxRTMPOutBuffer, which will increase the internal buffer used for the client connections.
You can read more about it in this post:
viewtopic.php?f=5&t=637&hilit=clientsidebuffer
Bryan