ADDITIONAL SYSTEM INFORMATION :
Windows 7 x64
java version 10.0.2

A DESCRIPTION OF THE PROBLEM :
When you collapse root tree - you will see that child treeItem graphics are still visible.

REGRESSION : Last worked in version 8u181

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
To reproduce just launch class below and expand/collapse root tree - you will see that child treeItem graphics are still visible.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
After collapsing root tree graphics of child treeItems should disappear

---------- BEGIN SOURCE ----------
package com.idc.shellexplorer;

import javafx.application.Application;
import javafx.beans.property.ReadOnlyStringWrapper;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TreeTableColumn;
import javafx.scene.control.TreeTableColumn.CellDataFeatures;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeTableView;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;
import javafx.scene.image.ImageView;

public class TestTreeTableView extends Application {


    public static void main(String[] args) {
        Application.launch(args);
    }

    @Override
    public void start(Stage stage) {
        stage.setTitle("Tree Table View Samples");
        final Scene scene = new Scene(new Group(), 200, 400);
        Group sceneRoot = (Group)scene.getRoot();


        //Creating the root element
        final TreeItem<String> root = new TreeItem<>("Root node", createIcon(Color.GREEN));

        for (int i = 1; i <= 30; i++) {
            //Creating tree items
            final TreeItem<String> childNode1 = new TreeItem<>("Child Node " + i);
            if (i % 2 == 0) {
                childNode1.setGraphic(createIcon(Color.BLUE));
            } else {
                childNode1.setGraphic(createIcon(Color.RED));
            }

            for (int j = 1; j <= 5; j++) {
                final TreeItem<String> childChildNode1 = new TreeItem<>("Child child Node " + j);
                childChildNode1.setGraphic(createIcon(Color.BLACK));
                childNode1.getChildren().add(childChildNode1);
            }
            root.getChildren().add(childNode1);
        }

        //Creating a column
        TreeTableColumn<String,String> column = new TreeTableColumn<>("Column");
        column.setPrefWidth(200);

        //Defining cell content
        column.setCellValueFactory((CellDataFeatures<String, String> p) ->
                new ReadOnlyStringWrapper(p.getValue().getValue()));

        //Creating a tree table view
        final TreeTableView<String> treeTableView = new TreeTableView<>(root);
        treeTableView.getColumns().add(column);
        treeTableView.setPrefWidth(200);
        treeTableView.setShowRoot(true);
        sceneRoot.getChildren().add(treeTableView);
        stage.setScene(scene);
        stage.show();
    }

    private ImageView createIcon(Color color) {
        return new ImageView(new Rectangle(12, 12, color).snapshot(null, null));
    }
}
---------- END SOURCE ----------

FREQUENCY : always