Why is a letter sent in a cycle 2 times to one addressee (loop iteration sticks)?

Question

PHP

Hello. I can’t understand anything, why some iterations are performed twice, written twice to the database and letters sent twice. I would also like to disconnect every 30 letters, for this I used $mail->SmtpClose(); in PHPMailer, but then something strange happens, the records in the database appear out of order (!), That is, not 1 2 3, but 1 3 2. Can anyone show the reason for this behavior? And how to do it all the same, so that letters would be sent 1 time, between each sending there was a pause of a second, and after 30 letters the connection was broken and there was a pause of 10 seconds and everything over again ..
I experimented many times, but did not achieve a meaningful result ...

<?php
$identNumber = 0;

// Generate UUID v4 function - needed to generate a CID when one isn't available
function gaGenUUID() {
    return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
            // 32 bits for "time_low"
            mt_rand(0, 0xffff), mt_rand(0, 0xffff),
            // 16 bits for "time_mid"
            mt_rand(0, 0xffff),
            // 16 bits for "time_hi_and_version",
            // four most significant bits holds version number 4
            mt_rand(0, 0x0fff) | 0x4000,
            // 16 bits, 8 bits for "clk_seq_hi_res",
            // 8 bits for "clk_seq_low",
            // two most significant bits holds zero and one for variant DCE1.1
            mt_rand(0, 0x3fff) | 0x8000,
            // 48 bits for "node"
            mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
    );
}

foreach ($mails as $sendMail) {
      
    $gcid = gaGenUUID();
    $mailadressant = $sendMail;
  $message = $mailtemplate;
  $mail->ClearAllRecipients();
  $mail->ClearCustomHeaders();
  $mail->setFrom('[email protected]', 'From mail');
  $mail->addReplyTo('[email protected]', 'From mail');
    $mail->Subject = "Тема письма";
    $mail->CharSet = 'UTF-8';
  $mail->isHTML(true);
  $mail->Body = $message;
  $mail->AltBody = $message;
  $mail->addAddress($mailadressant);     // Add a recipient
  $mail->addCustomHeader('List-Unsubscribe', 'http://mail.ru/uns.php');

    if (!$mail->send()) {
      $maillogstatus = 'Mailer Error: ' . $mail->ErrorInfo;
    } else {
      $maillogstatus = "ok";
    }
    sleep(1);
    
    $sendQuery = ('INSERT INTO mail_log ( log, maillogstatus ) VALUES( ?, ? )');
    $params = array( $mailadressant, $maillogstatus);
    insertDB($sendQuery, $params);
    
    if ($identNumber % 30 == 0) {
      //$mail->SmtpClose();
      sleep(10);
    }

      
        $identNumber = $identNumber + 1;

}
echo "done";