Double click prevention on form submission ignoring callback in forms with multiple submit buttons

According to me. you can do like this as well.

<?php
function mymodule_custom_form($form, &$form_state) {
$form['submit_calback_a']['1'] = array(
      '#type' => 'submit',
      '#value' => 'calback_a',
      '#attributes' => array(
        'class' => array('btn-link'),
        'title' => t('calback_a'),
      ),
    );

 $form['submit_calback_b']['1'] = array(
      '#type' => 'submit',
      '#value' => 'calback_b',
      '#attributes' => array(
        'class' => array('btn-link'),
        'title' => t('calback_b'),
      ),
    );

   $form['submit_calback_c']['1'] = array(
      '#type' => 'submit',
      '#value' => 'calback_c',
      '#attributes' => array(
        'class' => array('btn-link'),
        'title' => t('calback_c'),
      ),
    );
}

function mymodule_custom_form_submit($form, &$form_state) {
  $values = $form_state['values'];
  if ($values['op'] == t('calback_a')) {
      calback_a();
  }
  if ($values['op'] == t('calback_b')) {
      calback_b();
  }
  if ($values['op'] == t('calback_c')) {
      calback_c();
  }
}

Thanks for reporting this @jlopes23.

I have tested this manually on clean Drupal 7.98 install with a simple form (code you provided) and it seems like the correct submit handlers are called. Can you please test this with a simple custom form containing only the code you provided, if it is still a problem?