Deletes malformed unserilized post metas (schemas and robots

delete_metas.php

<?php
add_filter('the_content', function ( $content ) {
    global $wpdb;
	
	
	$sql = "
    SELECT * FROM {$wpdb->postmeta}
	WHERE `meta_key` LIKE '%rank_math_robots%'
	LIMIT 50
    ";

    $robots = $wpdb->get_results($sql);
    foreach ( $robots as $robot ) {
        $value = unserialize( $robot->meta_value );

        if ( is_array( $value ) ) continue;
        
        delete_metadata_by_mid( 'post', $robot->meta_id );
    }
	
	

    $sql = "
    SELECT * FROM {$wpdb->postmeta}
	WHERE `meta_key` LIKE '%rank_math_schema%'
	LIMIT 50
    ";

    $schemas = $wpdb->get_results($sql);

    foreach ( $schemas as $schema ) {
        $schema_array = unserialize($schema->meta_value);

        if ( is_array($schema_array) ) continue;
       $del =  delete_metadata_by_mid( 'post', $schema->meta_id );
    }
    return $content;
}, 10, 1);