Basically, if you get Sftp/FtpException, the only reasonable thing you can do is to dispose the client object and reinitialize the connection.
The only case you can continue working with the client object is ProtocolError status, which means that the server is not able to perform requested operation, but the connection is still valid and the client recovered from error in safe way.
E.g. access denied, file does not exists on remote, etc.
For more information about exceptions thrown by Rebex components, please see also this thread.