Timeout properties are ignored when connecting via a proxy

The problem is that we have a slow sftp server which takes some time to establish connection with. It may take up to 2 minutes to establish a connection, and after that it works fine. When connecting using various ftp-clients we increased timeout property and it worked for us.
However this does not work via the code. When trying to connect via a secured proxy - it seems that both
ConnectionInfo.Timeout and SftpClient.OperationTimeout have no effect and connection is terminated due to a timeout after ~27 seconds.
This seems to be an old issue with at least one other user facing it in 2015
http://stackoverflow.com/questions/34388446/c-sharp-renci-sshnet-sftp-client-connection-behind-proxy-timeout#comment72017745_34388446
For me it the same with Renci.SSH 2014 as well as with the latest version SSH.NET.2016.0.0

Thank you in advance for your consideration of the issue

Empieza por rastrear cómo las conexiones proxy gestionan ConnectionInfo.Timeout y SftpClient.OperationTimeout, y después reproduce el fallo informado con un servidor SFTP lento. Comprueba por qué la conexión termina después de unos 27 segundos a pesar de los valores configurados. Se considera completado cuando se respeta el timeout configurado al conectarse a través de un proxy seguro.