The ProxySG by default accepts Raptor FTP login syntax but there is a need to change it to Checkpoint.
This change can only be done via Command Line Interface (CLI). See example below:
ProxySG#(config)ftp login-syntax ?
raptor Set FTP login format to RAPTOR
checkpoint Set FTP login format to CHECKPOINT
ProxySG#(config)ftp login-syntax raptor
ok
ProxySG#(config)ftp login-syntax checkpoint
ok