The issue can be reproduced using a simple program (see below):

import javax.swing.*;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.util.concurrent.locks.LockSupport;

public class JTextFieldWithDelayTest {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame();
            JTextField textField = new JTextField(20);
            textField.addKeyListener(new KeyAdapter() {
                @Override
                public void keyTyped(KeyEvent e) {
                    LockSupport.parkNanos(1_000_000_000L);
                }
            });
            frame.add(textField);
            frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        });
    }
}

After launching the program, perform the following steps:
1) Switch to 'Spanish (United States)' input method (with 'Latin American' keyboard layout)
2) Type the following in a text field: ' ' o - i.e. single quote two times (using [ key on US keyboard) then o character.

Expected result is ''o.
Actual result is ''��.