I have reseted PHP to default condition, replaced file php.ini from the server, where the scan is working fine. Here is the log:
[Oct 16 14:11:01] Scan engine received request.
[Oct 16 14:11:01] Fetching stored cronkey for comparison.
[Oct 16 14:11:01] Checking cronkey: 5090ad8cbdec18062057862f4aa21add (expecting 5090ad8cbdec18062057862f4aa21add)
[Oct 16 14:11:01] Checking saved cronkey against cronkey param
[Oct 16 14:11:01] Checking if scan is already running
[Oct 16 14:11:01] Requesting max memory
[Oct 16 14:11:01] Setting up error handling environment
[Oct 16 14:11:01] Setting up scanRunning and starting scan
[Oct 16 14:11:01] Contacting Wordfence to initiate scan
[Oct 16 14:11:01] Calling Wordfence API v2.25:https://noc1.wordfence.com/v2.25/?k=40a20f1dd3198093ded96ff0475885c5fd30e60f3efc274d865377e5b7c593a1ac1e140bfad10eea9d7071ff3e9ad02656218f015c5d1bd7c3a129c615c44889&s=eyJ3cCI6IjQuOS44Iiwid2YiOiI3LjEuMTUiLCJtcyI6ZmFsc2UsImgiOiJodHRwczpcL1wvZG5pb2toLmdvdi51YSIsInNzbHYiOjI2ODQ0MzgzOSwicHYiOiI1LjYuMzgiLCJwdCI6ImNnaS1mY2dpIiwiY3YiOiI3LjI5LjAiLCJjcyI6Ik5TU1wvMy4yOC40Iiwic3YiOiJBcGFjaGVcLzIuNC42IChDZW50T1MpIG1wbS1pdGtcLzIuNC43LTA0IE9wZW5TU0xcLzEuMC4yay1maXBzIFBIUFwvNS40LjE2IiwiZHYiOiI1LjUuNTYtTWFyaWFEQiJ9&betaFeed=0&action=log_scan
[Oct 16 14:11:09] Got value from wf config maxExecutionTime: 10
[Oct 16 14:11:09] getMaxExecutionTime() returning config value: 10
[Oct 16 14:11:25] Forking during hash scan to ensure continuity.
[Oct 16 14:11:25] Entered fork()
[Oct 16 14:11:25] Calling startScan(true)
[Oct 16 14:11:25] Got value from wf config maxExecutionTime: 10
[Oct 16 14:11:25] getMaxExecutionTime() returning config value: 10
[Oct 16 14:11:32] Test result of scan start URL fetch: array ( ‘headers’ => Requests_Utility_CaseInsensitiveDictionary::__set_state(array( ‘data’ => array ( ‘server’ => ‘nginx/1.12.2’, ‘date’ => ‘Tue, 16 Oct 2018 11:11:31 GMT’, ‘content-type’ => ‘text/html; charset=UTF-8’, ‘x-powered-by’ => ‘PHP/5.6.38’, ‘x-robots-tag’ => ‘noindex’, ‘x-content-type-options’ => ‘nosniff’, ‘expires’ => ‘Wed, 11 Jan 1984 05:00:00 GMT’, ‘cache-control’ => ‘no-cache, must-revalidate, max-age=0’, ‘x-frame-options’ => ‘SAMEORIGIN’, ‘referrer-policy’ => ‘strict-origin-when-cross-origin’, ‘strict-transport-security’ => ‘max-age=31536000;’, ‘content-encoding’ => ‘gzip’, ), )), ‘body’ => ‘WFSCANTESTOK’, ‘response’ => array ( ‘code’ => 200, ‘message’ => ‘OK’, ), ‘cookies’ => array ( ), ‘filename’ => NULL, ‘http_response’ => WP_HTTP_Requests_Response::__set_state(array( ‘response’ => Requests_Response
[Oct 16 14:11:32] Starting cron with normal ajax at URL https://dniokh.gov.ua/wp-admin/admin-ajax.php?action=wordfence_doScan&isFork=1&scanMode=custom&cronKey=6fc060c4153658f16ff6ad6019bab0a9
[Oct 16 14:11:37] Scan process ended after forking.