java可视化bug！控件在设置背景透明后，可视化窗口会不断地重复绘制控件

bug不太好描述，就是我将一个JComboBox的选项背景设为了透明，然后发现我打开它的选项后，它会不断地在选项部分重复绘制鼠标刚才经过的控件，见gif（我并没有点击button，只是鼠标经过）

import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JTextField;
import java.awt.Color;
import java.awt.Component;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import java.awt.BorderLayout;
import javax.swing.JButton;

public class Try {

    private JFrame frame;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Try window = new Try();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public Try() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.getContentPane().setBackground(new Color(135, 206, 250));
        
        JComboBox<String> comboBox = new JComboBox<String>();
        comboBox.addItem("1");
        comboBox.addItem("2");
    
        comboBox.setEditable(true);
        JTextField boxField = ((JTextField)comboBox.getEditor().getEditorComponent());
        boxField.setBackground(new Color(0, 0, 0, 0));
        comboBox.setEditable(false);
        
        comboBox.setRenderer(new DefaultListCellRenderer() {
            
            @Override
            public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
                JComponent result = (JComponent)super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
                result.setOpaque(false);
                return result;
            }});
    
        frame.getContentPane().add(comboBox, BorderLayout.NORTH);
        JButton btnNewButton = new JButton("New button");
        frame.getContentPane().add(btnNewButton, BorderLayout.SOUTH);
        frame.setBounds(100, 100, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

请问怎么解决这个问题，让它的选项背景正常显示透明？