Remote Backup Error - "rsync lacks old-style"

Hi,

I can't make to work remote backups in my CWP with Centos 7

SSH connection is ok (in control panel and console using  ssh  -i /root/.ssh/backup/id_rsa myuser@myremotesshserver -p 22) but the backup fails.

If i throw a
php -d max_execution_time=1000000 -q /usr/local/cwpsrv/htdocs/resources/admin/include/cron_backup.php

I see multiple errors with:

rsync: This rsync lacks old-style --compress due to its external zlib.  Try -zz.
rsync error: syntax or usage error (code 1) at main.c(1585) [server=3.1.2]
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: error in rsync protocol data stream (code 12) at io.c(226) [sender=3.1.2]

i try it in 2 different ssh servers, with public key autentication connection working fine.

any help?

Thanks!

As update, today i made a new fresh Centos 7 fresh install. In this install, remote backups Works.

So, the problem was in two different ssh server, one a windows server SSH server install and other, a entware router ssh install. Seems that the rsync installed in these servers is not compatible with CWP remote backup task.