Gallery miniatures disappeared after saving the post

Temporary solution if anyone needs it:

to functions.php:

add_action('admin_enqueue_scripts', 'adminpanel_styles_and_scripts');
function adminpanel_styles_and_scripts() {
    wp_register_script('admin-custom-js', get_template_directory_uri() . '/js/admin.js', ['jquery']);
    wp_localize_script('admin-custom-js', 'wp_localize_data', ['ajax_url' => admin_url('admin-ajax.php')]);
    wp_enqueue_script('admin-custom-js');
}

add_action('wp_ajax_acfgalerie4_imgs_ids', 'acfgalerie4_imgs_ids_func');
add_action('wp_ajax_nopriv_acfgalerie4_imgs_ids', 'acfgalerie4_imgs_ids_func');
function acfgalerie4_imgs_ids_func() {
    $images_ids = explode(',', $_POST['images_ids']);
    $images_urls = array_map(function($image_id) {
        $image_url_medium = wp_get_attachment_image_url($image_id, 'medium');
        return $image_url_medium ?: wp_get_attachment_image_url($image_id, 'full');
    }, $images_ids);

    echo json_encode($images_urls);
    die;
}

to custom admin.js:

document.addEventListener('DOMContentLoaded', function() {
    acfgalerie4_thumbnails_fix();
});


function acfgalerie4_thumbnails_fix() {
    return new Promise((resolve, reject) => {
        let gallery_container = document.querySelector('.acf-galerie-4-container');
        if(!gallery_container) return;

        let images_containers = [...gallery_container.querySelectorAll('.attachment-thumbnail-container')];
        let images_ids = images_containers.map(container => container.dataset.id).join(',');

        let prepared_data = {
            action: 'acfgalerie4_imgs_ids',
            images_ids: images_ids
        }
        let data = new FormData();
        Object.entries(prepared_data).forEach(([key, value]) => data.append(key, value));

        fetch(wp_localize_data.ajax_url, {
            method: 'POST',
            body: data,
            headers: {
                'Cache-Control': 'no-cache',
            }
        }).then(responce => {
            if(responce.ok) {
                responce.json().then(data => {
                    let images_elems = images_containers.map(container => container.querySelector(':scope > img'));
                    if(!images_elems || !Array.isArray(data)) return;
                    images_elems.forEach((img_elem, index) => {
                        if(!data[index]) return;
                        img_elem.setAttribute('src', data[index]);
                    });
                });
            }
            else {
                console.log('responce: NOPE');
            }
        }).catch(error => {
            console.log('ERROR: ' + error);
        });
    });
}