How to fix malformed data in ACF field, caused by ACFML 1.6.0

functions.php

// edit: if you are using wp-cli, you can try to use this plugin https://github.com/OnTheGoSystems/acfml_fixer
// otherwise, please follow instructions below

// PLEASE READ ALL COMMENTS BEFORE RUNNING THIS SNIPPET
// ALSO  THE COMMENTS AT THE END OF THIS SNIPPET
//
// CREATE DATABASE BACKUP!
//
// update ACFML to the version 1.6.1, you can find it in wpml.org > my account > downloads
// add the whole snippet to your functions.php in theme directory and visit any page of your blog/site
function fix_json_like_fields( $start_id = 0, $end_id = 1000 ) {
    global $wpdb;
    $query = $wpdb->prepare( "SELECT * FROM {$wpdb->postmeta} WHERE post_id > %d AND post_id <= %d", $start_id, $end_id );
    $metas = $wpdb->get_results( $query );
    foreach ( $metas as $meta ) {
        if ( strpos( $meta->meta_key, "_" ) === 0 ) {
            continue;
        }
        $meta_value = maybe_unserialize( $meta->meta_value );
        if ( is_array( $meta_value ) && isset( $meta_value[ $meta->meta_key ] ) ) {
	        update_post_meta( $meta->post_id, $meta->meta_key, array_pop( $meta_value[ $meta->meta_key ] ) );
        }
    }
}

// call this function:
fix_json_like_fields();
// the function by default fixes data in post with id between 1 and 1000
// if you have more posts, change function to:
// fix_json_like_fields( 1000, 2000);
// and call again and repeat for next group of posts as long as all data will not be fixed