Why are letters not being searched in the mailbox?

Question

PHP

I'm looking for letters by imap, it works every other time, sometimes it finds it, sometimes it's an empty array and notice.
Mail for Yandex domain, authorization via application password. Through the so-called. the portal password is the same.

subject tried both in Latin and in another windows-1251 encoding, everything is the same.

Tried different versions of php, from 7.0 to 7.4, same thing.

php:

$folder = mb_convert_encoding('Название папки в почте', "UTF7-IMAP", "utf-8");

$imapPath = '{imap.yandex.ru:993/imap/ssl}' . $folder;
$login = '[email protected]';
$password = 'password';

$connection = imap_open($imapPath, $login, $password);

$messageNumbers = imap_sort(
  $connection,
  SORTDATE,
  1,
  0,
  'SUBJECT "прайс"',
  "UTF-8"
);

var_dump($messageNumbers);

conclusion:

array(0) {
}
PHP Notice:  Unknown: [UNAVAILABLE] SEARCH Backend error. sc=6nIoVY81NOs1_110949_2-c5e3fad6bae7 (errflg=2) in Unknown on line 0

Answer 1

The problem disappeared by itself, I suspect that Yandex fixed something there