Weird checkbox behaviour on WP 7

Hey, I hope this is the right place to report this but I am suspecting that the backend UI change broke something about CMB2 checkboxes. We are using CMB2 as a composer package in our plugin and the checkboxes behave weirdly in the newest RC of WordPress 7.

I also tested it on bare CMB2 and made a little video to illustrate the issue. Here are the steps to reproduce the issue:

1. Start WP instance on 7.0 Beta 6
2. Install CMB2 plugin
3. Add following code snippet:

add_action( 'cmb2_admin_init', 'cmb2_sample_metaboxes' );
/**
 * Define the metabox and field configurations.
 */
function cmb2_sample_metaboxes() {

	/**
	 * Initiate the metabox
	 */
	$cmb = new_cmb2_box( array(
		'id'            => 'test_metabox',
		'title'         => __( 'Test Metabox', 'cmb2' ),
		'object_types'  => array( 'page', ), // Post type
		'context'       => 'normal',
		'priority'      => 'high',
		'show_names'    => true, // Show field names on the left
		// 'cmb_styles' => false, // false to disable the CMB stylesheet
		// 'closed'     => true, // Keep the metabox closed by default
	) );

	// Regular text field
	$cmb->add_field( array(
		'name'       => __( 'Test Checkbox', 'cmb2' ),
		'desc'       => __( 'field description (optional)', 'cmb2' ),
		'id'         => 'test_checkone',
		'type'       => 'checkbox',
	) );

	// Regular text field
	$cmb->add_field( array(
		'name'       => __( 'Test Checkbox two', 'cmb2' ),
		'desc'       => __( 'field description (optional)', 'cmb2' ),
		'id'         => 'test_checktwo',
		'type'       => 'checkbox',
	) );

	// Add other metaboxes as needed

}

4. Edit page and observe weird behaviour in metabox as shown in the video.

Thank you!

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