Wing FTP Software

With wing ftp server Version 4.7.1 we get a lot of ssh_log_warnings:
[2016/04/22 16:13:16.280299, 1] ssh_socket_exception_callback: Socket exception callback: 1 (0)
[2016/04/22 16:13:16.280586, 1] ssh_socket_exception_callback: Socket error: disconnected
With older versions we don't have such errors.
What can I do to fix this Problem?

The file "ssh_log_warnings" just records something about SFTP activities, and there is no need to take care about it.