After updating RA-FTP from 11.2 to 12.3 the connection to the WS_FTP SFTP server doesn't work anymore.
If we would disable zlib compression on the FTP server (WS_FTP from IPSWITCH, latest version), the RA.FTP Agent would be able to connect again.
This is a bug
Release : 12.3
Component : RA FTP
This is a bug. A fix will be provided in a future version of the RA.