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.
A problem was solved where an error occurred during file transfer using the zlib compression.
Release : 12.3
Component : RA FTP
Update to a fix version listed below or a newer version if available.
RA.FTP v4.1.1 - Available