[SplitPane] Pixels cut off when GridPane inside SplitPane

I have a GridPane with 2 children (in 2 columns, each 50% wide), itself inside a SplitPane. For some application widths, the right-most pixels of the right child of the grid pane are cut off.

See the attached application. Note that when changing the width of the application, the right-border sometimes vanishes.

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Ok so I can't attach stuff. I'm pasting the code here.

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package gridpanebug;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class GridPaneBug extends Application {

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

    @Override
    public void start(final Stage stage) throws Exception {

        final Parent parent = FXMLLoader.load(getClass().getResource("GridPaneBug.fxml"));
        stage.setScene(new Scene(parent, 1024, 768));
        stage.show();
    }
}

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

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

<SplitPane xmlns:fx="http://javafx.com/fxml" style="-fx-padding: 20;">
<items>
<GridPane fx:id="gridPane" hgap="10">

<StackPane fx:id="firstChild" GridPane.columnIndex="0" GridPane.rowIndex="1" GridPane.vgrow="ALWAYS" style="-fx-border-color: black;"/>
<StackPane fx:id="secondChild" GridPane.columnIndex="1" GridPane.rowIndex="1" GridPane.vgrow="ALWAYS" style="-fx-border-color: black;"/>

<columnConstraints>
<ColumnConstraints percentWidth="50" />
<ColumnConstraints percentWidth="50" />
</columnConstraints>

</GridPane>
</items>
</SplitPane>