During the update, the admin panel doesn’t work and there’s a white screen

When updating Osclass to version Osclass v8.4.0, the admin panel is not working, I can’t log in! There’s a white screen, and the following error appears in the logs:

PHP Fatal error: Uncaught ValueError: Unknown format specifier "\xd1" in /var/www/admin/data/www/aviros.ru/oc-admin/themes/omega/items/index.php:40\nStack trace:\n#0 /var/www/admin/data/www/aviros.ru/oc-admin/themes/omega/items/index.php(40): sprintf('%\\xD1\\x81 - %\\xD1\\x81', '\\xD0\\xA3\\xD0\\xBF\\xD1\\x80\\xD0\\xB0\\xD0\\xB2\\xD0\\xBB\\xD0\\xB5\\xD0...', '\\xD0\\x90\\xD0\\xB2\\xD0\\xB8\\xD1\\x80\\xD0\\xBE\\xD1\\x81-\\xD0\\x9E...')\n#1 /var/www/admin/data/www/aviros.ru/oc-includes/osclass/classes/Plugins.php(67): customPageTitle('\\xD0\\x90\\xD0\\xB2\\xD0\\xB8\\xD1\\x80\\xD0\\xBE\\xD1\\x81-\\xD0\\x9E...')\n#2 /var/www/admin/data/www/aviros.ru/oc-includes/osclass/helpers/hPlugins.php(46): Plugins::applyFilter('admin_title', '\\xD0\\x90\\xD0\\xB2\\xD0\\xB8\\xD1\\x80\\xD0\\xBE\\xD1\\x81-\\xD0\\x9E...')\n#3 /var/www/admin/data/www/aviros.ru/oc-admin/themes/omega/parts/header.php(6): osc_apply_filter('admin_title', '\\xD0\\x90\\xD0\\xB2\\xD0\\xB8\\xD1\\x80\\xD0\\xBE\\xD1\\x81-\\xD0\\x9E...')\n#4 /var/www/admin/data/www/aviros.ru/oc-includes/osclass/helpers/hDefines.php(342): require('/var/www/admin/...')\n#5 /var/www/admin/data/www/aviros.ru/oc-admin/themes/omega/items/index.php(187): osc_current_admin_theme_path('parts/header.ph...')\n#6 /var/www/admin/data/www/aviros.ru/oc-includes/osclass/helpers/hDefines.php(342): require('/var/www/admin/...')\n#7 /var/www/admin/data/www/aviros.ru/oc-admin/items.php(768): osc_current_admin_theme_path('items/index.php')\n#8 /var/www/admin/data/www/aviros.ru/oc-admin/items.php(761): CAdminItems->doView('items/index.php')\n#9 /var/www/admin/data/www/aviros.ru/oc-admin/index.php(116): CAdminItems->doModel()\n#10 {main}\n thrown in /var/www/admin/data/www/aviros.ru/oc-admin/themes/omega/items/index.php on line 40, referer: <a href="https://aviros.ru/oc-admin/index.php?page=users&action=edit&id=4828">https://aviros.ru/oc-admin/index.php?page=users&action=edit&id=4828</a>

I have PHP version 8.4 installed.

It's issue with translation file. Ideally move your core translations out (tranlsation of _('% - %')  ... could be invalid in one of your catalogs)

Okay! I keep forgetting about this. Thank you so much! It helped.