I am currently working on isolating a bug using JDK 8 EA b102. It's very hard to break the issue down to its smallest form for the JavaFX teams to help diagnose the problem. I don't mind filing bugs, but it is difficult when you are deep into development and go for the upgrade (JDK 8 EA beta releases) to find out you are having weird behaviors. When I use prior versions of JDK8 this issue didn't happen. In a nutshell here is the issue:

I created a custom tabpane control using a StackPane to layer tabs.
Tab one (1st) has a content area with a clip region (vertical rectanglar viewport).
Tab two (2nd) has a content area having a JavaFX Circle node.
 
When I click on tab 2 the clip rect from Tab one is affecting the tab 2's content (clipping the circle).

Below are two scenarios which will help explore my issue further.

1.) When I comment out the statement below (located in Main.java start() method):
  primaryStage.initStyle(StageStyle.TRANSPARENT);

It works, however the native window decoration is not what I want for my app. After commenting the statement you'll get an OS native title bar, however the other expected behavior works (tab 1 is blue when selecting tab 2 and the circle is fully displayed.

2.) When I comment out the statement below (located in Main.java createTab1() method):
        tmpGroup.setClip(clip);

The clip object (Rectangle) is a viewport region for Tab 1 to display a VBox similar to a vertical carousel of icons giving the display a border like frame width for icons to scroll. After commenting out the statement above you will not see the clipping (you will see the whole icon area), but the other expected behaviors work (tab 1 is blue when selecting tab 2 and the circle is fully displayed.

I believe if this issue is acknowledged I can upload images and source code.