No Label on button:

    public void start(Stage stage) throws Exception {
        StackPane rootPane = new StackPane();
        Button letterButton = new Button("B");
        letterButton.setStyle("-fx-wrap-text: true");
        rootPane.getChildren().add(letterButton);
        Scene scene = new Scene(rootPane, 1200, 800);
        stage.setScene(scene);
        stage.show();
    }

This is only in the latest build, and used to work in the previous build so this is a backwards compatibility issue (and although innocent looking, completely kills my app that has a software keyboard in it).

This works on b13 and doesn't on the latest, I haven't tested any other versions.