Can not adjust Gridpane without GUI crashing.
Have to then force restart the GUI and only way to adjust Gridpane is to remove the top component (IE top gridpane row)
When re-adding the row it becomes unstable and unpredictable.

Gridpanes are always an issue for me. When I am working with them I will save EVERY time I make a change as it is unpredictable as to when it will crash. Usualyy a restart of the GUI will allow a continuation of work for a bit of time until the next crash.

This current problem is different as it is occurring every time I try to adjust the height of the top row of the Gridpane, whether the absolute height or as a percentage.
The FXML code is posted below.

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane id="AnchorPane" prefHeight="608.0" prefWidth="794.0" xmlns:fx="http://javafx.com/fxml" fx:controller="mysqletl.mainController">
  <children>
    <Label fx:id="label" layoutX="126.0" layoutY="120.0" minHeight="16.0" minWidth="69.0" />
    <GridPane prefHeight="608.0" prefWidth="794.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
      <children>
        <TableView fx:id="tbl_original" prefHeight="200.0" prefWidth="200.0" GridPane.columnIndex="1" GridPane.rowIndex="1">
          <columns>
            <TableColumn prefWidth="75.0" text="Column X" />
          </columns>
        </TableView>
        <TableView fx:id="tbl_transformed" prefHeight="200.0" prefWidth="200.0" GridPane.columnIndex="1" GridPane.rowIndex="2">
          <columns>
            <TableColumn prefWidth="75.0" text="Column X" />
            <TableColumn prefWidth="75.0" text="Column X" />
          </columns>
        </TableView>
        <VBox prefHeight="166.0" prefWidth="97.0" GridPane.columnIndex="0" GridPane.rowIndex="1">
          <children>
            <VBox prefHeight="200.0" prefWidth="100.0">
              <children>
                <Button mnemonicParsing="false" onAction="#handleButtonAction" text="Extract Duplicates" />
                <Button mnemonicParsing="false" text="Extract empties" />
                <Button mnemonicParsing="false" text="Extract format" />
              </children>
            </VBox>
            <VBox prefHeight="200.0" prefWidth="100.0">
              <children>
                <Button mnemonicParsing="false" onAction="#MaskButtonAction" text="Mask" />
              </children>
            </VBox>
          </children>
        </VBox>
        <VBox prefHeight="200.0" prefWidth="100.0" GridPane.columnIndex="0" GridPane.rowIndex="2">
          <children>
            <VBox prefHeight="200.0" prefWidth="100.0">
              <children>
                <Button mnemonicParsing="false" text="Make Original" />
              </children>
            </VBox>
            <VBox prefHeight="200.0" prefWidth="100.0">
              <children>
                <Button mnemonicParsing="false" text="Reset" />
              </children>
            </VBox>
          </children>
        </VBox>
      </children>
      <columnConstraints>
        <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" percentWidth="15.0" prefWidth="100.0" />
        <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
      </columnConstraints>
      <rowConstraints>
        <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
        <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
        <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
      </rowConstraints>
    </GridPane>
  </children>
</AnchorPane>