Date picker libraries are missing in specific page
Do you have a custom theme? If so, the easiest way to ensure jquery.ui.datepicker loads on every page is to list it as a dependency in your theme libraries file. E.g. 

# @file /themes/custom/my_theme/my_theme.libraries.yml

# My theme global library.
global:
  js:
    js/my_theme.js: {}
  css:
    theme:
      css/my_theme.css: {}
  dependencies:
    - core/jquery
    - ...
    - core/jquery.ui.datepicker


Alternatively, you can add it via a theme or custom module.

/**
 * Implements hook_preprocess_page().
 */
function my_theme_or_module_preprocess_page(&amp;$variables) {
  $variables['#attached']['library'][] = 'core/drupal.date';
}