Reset 'uptodate' flag of all translations if page is saved in default language via kirby panel

translations.php

<?php

kirby()->hook('panel.page.update', function($page) {
  // only trigger if page has default language
  if (site()->language()->code() == site()->defaultLanguage()->code()) {
    foreach(site()->languages() as $language) {
      // don't reset default language itself
      if ($language->code() == site()->defaultLanguage()->code()) {
        continue;
      }
      
      try {
        $page->update(array(
          'translations' => 0, // change 'translations' to the name of your field
        ), $language->code());
      } catch(Exception $e) {
        echo $e->getMessage();
      }
    }
  }
});