ADDITIONAL SYSTEM INFORMATION :
Windows 7 x64
java 10.0.2


A DESCRIPTION OF THE PROBLEM :
When you expand the root treeItem and scroll down then up you will see that root treeItem graphic will be replaced with child treeItem graphic and one of child treeItem graphics will be replace with root TreeItem graphic.

REGRESSION : Last worked in version 8u181

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
To reproduce just launch class below, expand root tree, scroll down and then scroll up - you will see the mess with treeItem graphics

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
After scrolling root tree each treeItem will have its original graphic
ACTUAL -
After scrolling root tree some treeItems have not there original graphic

---------- 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);
            childNode1.setGraphic(createIcon(Color.BLUE));

            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