This most likely indicates that the default shell for the user on the FreeNAS 13 host is csh/tcsh.
If you change the default shell of the user being used for replication on the FreeNAS 13 box to /bin/sh, you should see the errors clear. If you can’t manage that, removing mbuffer on that system will decrease performance (due to lack of buffering on one end), but it will work around the issue of csh’s extremely stupid redirect handling. 