Theme hook suggestion causes machine_name error on forms with label defined

Problem/Motivation

I am not positive that this is a menu_block issue vs. Group issue, but:

When adding a derivative menu block into a form with a label field (for example: editing a Group, the Group name is 'label') the following error occurs:

LogicException: The machine name element "_field_][widget][2][settings][style][suggestion" is defined before the source element "label", it must be defined after or the source element must specify an id. in Drupal\Core\Render\Element\MachineName::processMachineName() (line 191 of /var/www/web/core/lib/Drupal/Core/Render/Element/MachineName.php).

In Core/Render/Element/MachineName.php - a check is performed if 'label' is set in the form, if it is then it checks for $source['#id'], if label exists and $source['#id'] doesn't then it returns the above exception. basic_page forms do not produce this error, but a Group form will.

Steps to reproduce

Add a Block(plugin) field to a Group, then add a menu_block derivative in the block field within the Group form and the ajax call will return a 500 error due to the MachineName exception.

Proposed resolution

Does the suggestion field need to be #type => machine_name? Testing locally I've been able to avoid the MachineName error by setting this field to #type => 'textfield'.

src/Plugin/Block/MenuBlock.php:

$form['style']['suggestion'] = [
'#type' => 'machine_name',
'#title' => $this->t('Theme hook suggestion'),
'#default_value' => $config['suggestion'],
'#field_prefix' => 'menu__',
'#description' => $this->t('A theme hook suggestion can be used to override the default HTML and CSS classes for menus found in menu.html.twig.'),
'#machine_name' => [
'error' => $this->t('The theme hook suggestion must contain only lowercase letters, numbers, and underscores.'),
'exists' => [$this, 'suggestionExists'],
],
];