Backup overwritten Synology does not support appending incremental info

Hi All,

Comodo Backup does not carry out a scheduled incremental backup due to: “Existing backup will be overwritten because this destination does not support appending incremental / differential information to same backup”.

The destination is a Synology DS412 ver 5.3 NAS for which I made a FTP login for CB.

I would like the incremental backup to work. What are your recommendations to achieve that?
Thanks in advance.