ACF 5.8-Beta-4.1: Some radio buttons values are not going to be retrieved in the editor and front-end

A very strange bug bugged me today.
I have a simple radio buttons field with values like:

• page
• icon
• link
• file

It occurs that the two last choices cannot be retrieved in ACF Beta 4.1. When I select one of them, save the page and reload, default choice (page) is selected. Also, there are errors in the console when loading.
When I switch to the code editor, the choice is saved as "mytest-section-type":"file"
It seems that words like link or file are somehow restricted when they are going to be displayed. Maybe there are more of such words (I checked 'text', 'url', 'email', but these are OK)?

/**
 * Test ACF blocks in 5.8-beta4
 */

add_action( 'acf/init', 'my_acf_blocks_init' );
function my_acf_blocks_init() {
	/**
	 * Register block
	 */
	acf_register_block_type( array(
		'name'            => 'mytest',
		'title'           => __( 'My Test Block', 'my-acf' ),
		'description'     => __( 'A block for testing ACF Beta.', 'my-acf' ),
		'render_callback' => 'my_acf_block_render_callback',
		'category'        => 'formatting',
		'icon'            => 'external',
		'keywords'        => array(),
		'supports'        => array( 'align' => false ),
		'mode'            => 'edit',
	) );

	/**
	 * Define block fields
	 */
	acf_add_local_field_group( array(
		'key' => "group_mytest",
		'title' => __( 'Block :: My Test Block', 'my-acf' ),
		'location' => array(
			array(
				array(
					'param' => 'block',
					'operator' => '==',
					'value' => 'acf/mytest',
				),
			),
		),
		'fields' => array(
			array(
				'key' => "field_mytest-section-type",
				'label' => __( 'Section type', 'my-acf' ),
				'name' => "mytest-section-type",
				'type' => 'radio',
				'choices' => array(
					'page' => __( 'Page', 'my-acf'),
					'icon' => __( 'Icon', 'my-acf'),
					'link' => __( 'Link', 'my-acf'),
					'file' => __( 'File', 'my-acf'),
				),
				'default_value' => 'page',
				'layout' => 'horizontal',
			),
		),
	) );
}

Use the supplied ACF block registration and radio-field example as the reproduction case. Start by tracing how the radio choices are rendered and restored in the block editor, then check the console errors when reloading; done means the link and file choices persist and are retrieved in both the editor and front end.