SQL Server Reporting Services in WebViews shows 401

FULL PRODUCT VERSION :
1.7_80
1.8_60
1.8_74


ADDITIONAL OS VERSION INFORMATION :
Windows Server 2012R2
Windows 8.1
Windows 7


A DESCRIPTION OF THE PROBLEM :
i use WebView to show SQL Server Reports (SSRS) for my warehouse management system
the SSRS uses HTTP Authentication (fix with Authenticator)

in 2 older System this works like espected
http://194.25.240.197:9980/ssrs.works.png
(uses java 1.7_x)

in the current system, we have made an upgrade to 1.8
i can open the Reports/ rendering is correctly
but after a whole time or change the settings ('Platz' / 'Intervall') or click on [View Report]
an 401 error occurs http://194.25.240.197:9980/ssrs.401.png

i have created an simply FX Browser test class
the problem only occures in Java 1.8:
1.8_60 -> 401
1.8_74 -> 401
1.7_80 -> works

how i can debug / log URL Connections from WebView

REGRESSION. Last worked in version 8u74

ADDITIONAL REGRESSION INFORMATION:
1.8_60 -> 401
1.8_74 -> 401
1.7_80 -> works


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
i use this test class
SQL Server Reporting Services

public class AmisTest extends Application {
/**
* @param args
*/
public static void main(String[] args) {
launch(AmisTest.class, args);
}

/**
* @see javafx.application.Application#start(javafx.stage.Stage)
*/
@Override
public void start(Stage primaryStage) throws Exception {
Authenticator.setDefault(new Authenticator() {
/**
* @see java.net.Authenticator#getPasswordAuthentication()
*/
@Override
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication("<user>", "<pw>".toCharArray());
}
});

final BorderPane root = new BorderPane();

final WebView webView = new WebView();
final WebEngine webEngine = webView.getEngine();
webEngine.setJavaScriptEnabled(true);
BorderPane.setMargin(webView, new Insets(2, 4, 4, 4));
root.setCenter(webView);

final TextField url = new TextField();
url.setOnAction(new EventHandler<ActionEvent>() {

@Override
public void handle(ActionEvent event) {
webEngine.load(url.getText());
}
});

BorderPane.setMargin(url, new Insets(4, 4, 2, 4));
root.setTop(url);

primaryStage.setTitle(System.getProperty("java.runtime.version"));
primaryStage.setScene(new Scene(root));
primaryStage.show();
}
}
---------- END SOURCE ----------