Symfony version(s) affected: 4.4.10

Description
I have a project on 4.4.8. I have a form with a compound child form. The child form will throw a TransformationFailedException for some missing fields. I updated and got v4.4.10. Somehow this is no longer works. Instead of the form being marked as invalid, the form is 'valid' as per $form->isSubmitted() && $form->isValid() but getData returns null.

How to reproduce
I'll work to create a reproducer and edit this.

Possible Solution
Not sure yet. I did a diff of the Form component and saw only minor changes so haven't isolated the issue yet.