Plugin to reproduce a bug that seems to toggle Admin Menu items, The whole post/post-new screen contents and user preferences for Screen Options (showing Meta Boxes). Everything needs confirmation. The plugin logs the responsible JavaScript Events to the console.

toggle_metabox_bug.php

<?php

namespace WCMTest;

defined( 'ABSPATH' ) OR exit;
/** Plugin Name: Toggle MetaBox: Bug Inspect */

\add_action( 'admin_menu', array( __NAMESPACE__.'\AddMetaBox', 'getInstance' ) );
class AddMetaBox
{
	public static $instance = null;

	public static function getInstance()
	{
		null === self::$instance AND self::$instance = new self;
		return self::$instance;
	}

	public function __construct()
	{
		\add_action( 'add_meta_boxes', array( $this, 'addMetaBox' ) );
		\add_action( 'admin_footer-post-new.php', array( $this, 'addDebugScript' ) );
	}

	public function addMetaBox()
	{
		\add_meta_box(
			\get_current_screen()->id,
			'MetaBox Test',
			array( $this, 'metaBoxContent' )
		);
	}

	public function metaBoxContent()
	{
		printf(
			'<pre>%s</pre>',
			htmlspecialchars( var_export( \get_current_screen(), true ) )
		);
	}

	public function addDebugScript()
	{
		$el = \get_current_screen()->id."-hide";
		?>
		<script type="text/javascript">
			"use strict";

			( function( $ ) {
				$( '#<?php echo $el; ?>' ).on( 'click', function( ev ) {
					$.each(
						$( '#<?php echo $el; ?>' ).data( 'events' ),
						function( i, e ) {
							console.log( i, e );
						}
					);
				} );
			} )( jQuery );
		</script>
		<?php
	}
}