Run the test case below, or any other drag and drop enabled Swing demo. Enter some text, drag it, and drop it in the window. The drop cursor flashes to NO_DROP temporarily. This is a very recent regression. However, it does NOT seem related to 4869264 which was recently putback. And it is NOT the same issue as 6388028 which talks about the drop cursor flashing when the action is changed.

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

public class DTest extends JFrame {
    
    public DTest() {
        super("DTest");
        
        JTextArea ta = new JTextArea();
        ta.setDragEnabled(true);
        getContentPane().add(new JScrollPane(ta));
    }

    private static void createAndShowGUI(String[] args) {
        DTest test = new DTest();
        test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        test.setSize(400, 400);
        test.setLocationRelativeTo(null);
        test.setVisible(true);
    }
    
    public static void main(final String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI(args);
            }
        });
    }
}