Nach deinem Log gehe ich davon aus, dass das lokale scp über ssh remote das Kommando "scp -v -t /i-data/ad15aede/backup/kate/" auf dem NAS ausführen will - und das erzeugt dann den Fehler.
Edit: aus dem Wikipedia-Artikel "Secure copy":
Normally, a client initiates an SSH connection to the remote host, and requests an SCP process to be started on the remote server. The remote SCP process can operate in one of two modes:
source mode, which reads files (usually from disk) and sends them back to the client, or
sink mode, which accepts the files sent by the client and writes them (usually to disk) on the remote host.
For most SCP clients, source mode is generally triggered with the -f flag (from), while sink mode is triggered with -t (to). These flags are used internally and are not documented outside the SCP source code.