This issue is reported against SWT:

https://bugs.eclipse.org/bugs/show_bug.cgi?id=207223

In a few words, they embed a text area into an SWT container using SWT_AWT bridge, and then show a dialog with yet another text area. Sometimes, when the dialog is shown, one text area or another are not editable as if the frame/dialog didn't have the input focus.

The source code to reproduce the problem is here:

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JPanel;
import javax.swing.JRootPane;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

import org.eclipse.swt.SWT;
import org.eclipse.swt.awt.SWT_AWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class PR207223 {
    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);

        shell.setLayout(new FillLayout());
        Composite composite = new Composite(shell, SWT.EMBEDDED);
        final Frame frame = SWT_AWT.new_Frame(composite);


        Panel panel2 = new Panel(new BorderLayout());
// JPanel panel1 = new JPanel();
        JRootPane panel1= new JRootPane();
        panel2.add(panel1);
        frame.setLayout(new FlowLayout());

        panel1.setLayout(new FlowLayout());
        JButton button = new JButton("Launch dlg");
        final JDialog dlg = new JDialog(frame);
        //
        dlg.setModal(true);
        dlg.setTitle("Swing JDialog");
        button.addActionListener( new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JPanel panel = new JPanel();
                panel.setLayout(new FlowLayout());
                JTextArea txtarea = new JTextArea(5, 20);
                JScrollPane scrollpane = new JScrollPane(txtarea);
                panel.add(scrollpane);

                JButton button = new JButton("Close");
                button.addActionListener( new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                        dlg.dispose();
                    }
                });
                panel.add(button);

                dlg.getContentPane().add(panel);
                dlg.pack();
                dlg.setVisible(true);
            }
        });
        panel1.add(button);

        JTextArea txtarea = new JTextArea(5, 20);
        JScrollPane scrollpane = new JScrollPane(txtarea);
        panel1.add(scrollpane);

        frame.add(panel2);
        frame.add(panel1);

        shell.setSize(400, 200);
        shell.setText("SWT_AWT main window");
        shell.open();
        while(!shell.isDisposed()) {
            if(!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();
    }
}