WordPress Custom Post Type is Matching on Partial Slug

I’m having a really weird issue. For example, there is a custom post ‘people’. The post title is the name of the person and pretty permalinks are enabled. Say we have a person custom post with the name of ‘John Smith’ with a slug of ‘john-smith’. If I visit the URL example.com/jo, it still redirects me to the URL example.com/john-smith.

I’ve never seen this behaviour in WordPress before. Does anyone know what might be causing it?

Add this code in your active theme’s functions.php file and it should stop WordPress guessing the source of the incomplete slug:

function no_redirect_guess_404_permalink( $header ){
    global $wp_query;

    if( is_404() )
        unset( $wp_query->query_vars['name'] );

    return $header;
}

add_filter( 'status_header', 'no_redirect_guess_404_permalink' );

Original answer here