SFTP upload to NAS: action timed out - np SYN even

I needed to switch my daily backup upload from ftp to sftp as the new NAS does not allow pure FTP (TLS/SSL required)



I am trying this, . the credentials work when used from a mac:

/tool fetch upload=yes url=“sftp://192.168.0.10/ftp/test.rsc” user=koerberGW password=“correct” src-path=“config-koerberGW-2023jun29-225844.rsc” src-address=192.168.0.1 port=22

which sadly hangs for a while (1 minute or so) and then throws:

action timed out - try again, if error continues contact MikroTik support and send a supout file (13)
action timed out - try again, if error continues contact MikroTik support and send a supout file (13)


Running a TCPDUMP on the NAS shows no connections, (not even a SYN packet) other than an ARP request for 192.168.0.10 which is answered,
so the issue must be on the RB.

At the same time syslog to port 514 sends to the same NAS happily (as shown by the same tcpdump), so do pings.

setting
/system logging add topic=ssg,!packet
only shows a lot of peer channel #0 window messages, but no key exchange or other SSH/SFTP details

This is on an old RB2011iL running the latest 6.49.8

I am stumped
I tried various combinations of the parameters (with explicit dest-path, etc) to no avail

Any ideas what could cause this / how to solve it?

thanks