LogicException: The database connection is not serializable.

Hi,

Im not sure if anyone else has got this error or not, but when I try to perform a validation $form_state->setErrorI am getting an error 

LogicException: The database connection is not serializable. This probably means you are serializing an object that has an indirect reference to the database connection. Adjust your code so that is not necessary. Alternatively, look at DependencySerializationTrait as a temporary solution. in Drupal\Core\Database\Connection->__sleep()

I will explain a bit more. In my form I have a form element which has an "Add more" functionality. That is, I can add another instance of that field with an incremented index in its name which is working all fine. Now I have added a form validation and want to validate against all the instances of this field. Its a straight forward validation logic

if (empty($field)) {
  $form_state->setError($form['content_bag_container']['bag_wrapper'][$key]['content_bag'], t('Please enter a content bag name.'));
}

Weirdly enough, this validation works for the first instance of the form element which pre-loads with the page itself. But whenever, I create a new instance via ajax, this validation fails and throws this error message in the log.

Can anyone check if this is some problem from my end or a bug in the core, cause I am not sure if an ajax populated field should be validated separately.

Thanks in advance...