Hi!

I'm not sure if it is a bug or intentional, but in bootstrap4 form layout the validation errors are rendered inside the label tag see:
https://github.com/symfony/twig-bridge/blob/master/Resources/views/Form/bootstrap_4_layout.html.twig#L206

It's not exactly how bootstrap recommends it.
https://getbootstrap.com/docs/4.0/components/forms/#validation

Regards,
Marton