error creating a custom field group

Hello seem to be a bug while creating a custom field group.
The error seem to be when assigning custom field group to 'attachment' post type AND with the parameter 'media_modal' => true.

The result is: the custom field is not saving to database and other strange error if you assign to other post types together

I think that the problem is in html rendered.
Please look at this image: https://ibb.co/k5cv6Ds

a simple php code of creating custom field group:

$meta_boxes[] = [
	'id' => 'attachment_cf',
	'title' => 'Campi extra',
	'post_types' => 'attachment',
	//'context' => 'normal',
	//'style' => 'default',
	//'closed' => false,
	//'priority' => 'high',
	//'default_hidden' => false,
	//'autosave' => false,
	'media_modal' => true,
	'class' => '',
		
	//Campi
	'fields' => array(
		
		//Url alternativo
		[
			'name' 					=> 'Url alternativo',
			'id'					=> 'url_alt_webp',
			'type'					=> 'text',
			//'readonly' 				=> 'false'
		],			
		
	)
];