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

Inizia tracciando il modo in cui le connessioni proxy gestiscono ConnectionInfo.Timeout e SftpClient.OperationTimeout, quindi riproduci il problema segnalato con un server SFTP lento. Verifica perché la connessione termina dopo circa 27 secondi nonostante i valori configurati. Il lavoro è completato quando il timeout configurato viene rispettato durante la connessione tramite un proxy sicuro.