Remote Side unexpectedly closed network connection

Hi Team,
Getting error while connecting winscp .Please see the attached screen shoot , username and password is correct , it happen some times when i m not able to connect while my team mates able to connect . Please see attached screen shot.

Have you checked server log files or have you contacted the server administrator?

I m Server Administrator , There is no issue with connection with port/credentials etc.
Do you want to check server logs , if yes there is nothing .

At the moments you are not able to connect with WinSCP, can you connect with any other SSH/SFTP client?