Pull replication over ssh is failing between a FreeNAS-11.3-U4.1 source and a FreeNAS-11.3-U5 target. I believe this was broken when both were running FreeNAS-11.3-U4.1.
It looks like zfs sends snapshots from source to target and that replication_task__task_1.progress_observer measures progress by running a ps on the source:
Running ['ps', '-o', 'command', '-p', '20943']
without an = suffix to the "command" keyword ps produces two lines of output:
"COMMAND\nzfs: sending hostname....o-2020-11-03_15-00 (71%: 197 \n"
"COMMAND\nzfs: sending hostname....o-2020-11-03_15-00 (96%: 197 \n"
etc. rather than just the snapshot name and progress. The pull then fails:
[replication_task__task_1.progress_observer] [zettarepl.transport.progress_report_mixin] Unable to find ZFS send progress in 'COMMAND\nzfs: sending hostname....o-2020-11-03_16-00 (6%: 3771 \n'