Premature end of script headers

Hello,
My website is hosted in a VPS. I get some errors like below. I cannot pass this problem. Could you share with me any suggesstion to solve this problem, please?
Thank you in advance.

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Premature end of script headers: admin-ajax.php, referer: https://cyberonboard.com/wp-admin/
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Premature end of script headers: wp-cron.php, referer: https://cyberonboard.com/wp-cron.php?doing_wp_cron=1544561618.8827359676361083984375