radio button default value not set

I am experiencing the same issue. Boolean field with on off checkbox. Setting the default to be on (checked) doesn't default the field to be checked on the checkout pane.

As a workaround I ended up setting the default value to 1 (checked) in a hook_form_alter in my custom module. Here is the code.

function YOUR_MODULE_form_alter(&$form, &$form_state, $form_id) {
   if($form_id == 'commerce_checkout_form_checkout') {
      $form['commerce_fieldgroup_pane__group_YOUR_FIELDGROUP']['field_YOUR_FIELD']['und']['#default_value'] = 1;
   }
}