JCheckBox and JRadioButton components have image and text rendering.
For bug isolation, I have set text to empty string. So, this has to do with image rendering sequence.

Steps to reproduce -
Launch the test program given here and click on JCheckBox and JRadioButton alternately. Keep on observing state of these components on every click. Sometime, the state (checked/unchecked) image gets into inconsistent state.
Do a refresh by switching focus away from the test window and get back to it. The checked/unchecked state recovers.

Test program ------

import java.awt.FlowLayout;
import javax.swing.JFrame;
import javax.swing.JRadioButton;
import javax.swing.JPanel;
import javax.swing.JCheckBox;

class CheckBoxTest extends JFrame {
    static JFrame f;

    public static void main(String[] args)
    {
        f = new JFrame();
        f.setSize(300, 300);
        f.setLayout(new FlowLayout());


        JCheckBox c = new JCheckBox("");
        JRadioButton b = new JRadioButton("");

        JPanel p = new JPanel();
        p.add(b);
        p.add(c);

        f.add(p);

        f.setVisible(true);
    }
}

Tip : I was able to reproduce this using mouse click on touchpad of my macbook pro.
Sometimes it takes a while to reach this inconsistent state with this program.

Same issue can be seen with SwingSet2- https://bugs.openjdk.java.net/browse/JDK-8236592