This is the Result of the bug fix 6514599

import java.awt.*;
import javax.swing.*;

public class JSpinnerBug2
{
    public static void main(String[] args)
    {
        // create a JSpinner and set a value
        JSpinner spinner = new JSpinner();
        spinner.setValue(new Integer(1234567890));
        
        // get the arrow buttons
        Component arrowUp = spinner.getComponent(0);
        Component arrowDown = spinner.getComponent(1);
        
        // try remove both buttons from the layout
        LayoutManager layout = spinner.getLayout();
        layout.removeLayoutComponent(arrowUp);
        layout.removeLayoutComponent(arrowDown);
        
        // create a frame and add the spinner spinner
        JFrame frame = new JFrame("Only the arrow down is missing");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Container pane = frame.getContentPane();
        pane.setLayout(new FlowLayout());
        pane.add(spinner);
        
        // show the frame
        frame.setBounds(0, 0, 300, 150);
        frame.setVisible(true);
    }
}

Run the this above stated test on the Metal LAF. Now look at the right side of the Spinner, the border is missing.