Hi,
Pulling a stream from the same port shouldn’t be a problem.
The "Back timestamp" errors may be caused by lost packets due to network congestion. The total bandwidth of the input streams could be larger than the I/O capability of the network hardware between the EMS and the encoder. You may need to upgrade your network card(s) and/or router(s) to meet the bandwidth requirements of your input streams.
Cheers,
Don