Backup config files to FTP server Failed to read reply to QUIT

SYSTEM INFORMATION
OS type and version Debian GNU/Linux 12 (bookworm)
Webmin version 2.202

I’m trying to backup configuration files from webmin to a NAS in my office through FTP.
I’ve configured everything and I get this error:
Failed to read reply to QUIT

Logs on the FTP server don’t show anything wrong. It just says connection successful

I’m using default port 21 and I have passive ports turned ON on the NAS.

I haven’t had a problem with other plesk servers (using FTPS) nor FileZilla.

I’ve tried different ports, but get a different error:
port 9333 initial connection failed : 2.0-OpenSSH_8.3
port 990 Failed to IPv6 connect to *********.myddns.me:990 : Connection refused it’s an ipv4 domain, don’t why it’s trying ipv6

I haven’t tried SSH as we’d prefer not to use that.

Github issue: Backup config files to FTP server error · Issue #2394 · webmin/webmin · GitHub