In my particular example (which I may or may not be able to extract and reproduce), I have:
In this example, the form's children are marked for deletion; then, when ValidatorTHDelegate sees that the parent is not a new component, it bails out, thus failing to invoke the next handler and re-add the child components. When the deletion is finalized the form is left with no children, which incidentally makes it impossible to complete the AJAX request as designed, since the component to re-render no longer exists! I believe this would only be a problem in wrapping mode. I have verified that removing the validateBean tag causes the form's structure to be preserved.