Multistep form loses input when visiting previous step
I think you should add if statement with #triggering_element or #clicked_button. Example:

function PREVIOUS_STEP_submission_OR_SOME_KIND_OF_CALLBACK($form, &amp;$form_state) {
  if($form_state['clicked_button']['#value'] == 'BACK') {
    //show_previous_step()
  }
  else {
    $a = new ind();
    $a-&gt;get_ind( $form_state['build_info']['args'][0] );

    $form_state['values'] = get_object_vars($a);
    unset($a);
    // or your logic
  }
}