Description:
------------
log bellow happens randomly, pages generated by php-fpm are cut after <80kb with ??? characters. there is no backtrace. nginx respond correctly without problems. This affects php files only. removed zip and zlib modules did not help. removing opscache do not help. nginx gzip disabled/enabled. changing fastcgi buffers did not help. this happpens on several servers it is not hardware related. nginx is in standard configuration. once php-fpm start to fail all server pages are failing, but nginx still produce 200 response.
restarting php-fpm helps. php.ini is in standard configuration. this start to happening from 7.0.16


[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80582 exited with code 0 after 0.005648 seconds from start
[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80584 started
[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80583 exited with code 0 after 0.005877 seconds from start
[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80585 started
[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80581 exited with code 0 after 0.007763 seconds from start
[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80586 started
[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80585 exited with code 0 after 0.005653 seconds from start
[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80587 started
[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80586 exited with code 0 after 0.005820 seconds from start
[18-Mar-2017 15:41:49] NOTICE: [pool www] child 80588 started



PHP 7.0.17 (cli) (built: Mar 17 2017 02:07:44) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
    with Zend OPcache v7.0.17, Copyright (c) 1999-2017, by Zend Technologies

pm = dynamic
pm.max_children = 25
pm.start_servers = 2
pm.min_spare_servers = 2
pm.max_spare_servers = 3
pm.max_requests = 0 ;changing to 500

[PHP Modules]
bcmath
bz2
Core
ctype
curl
date
dom
facedetect
fileinfo
filter
ftp
gd
geoip
hash
iconv
imagick
imap
json
libxml
mbstring
mcrypt
memcache
memcached
mongodb
mysqli
mysqlnd
openssl
pcntl
pcre
PDO
pdo_mysql
pdo_sqlite
Phar
posix
Reflection
session
SimpleXML
soap
sockets
SPL
sqlite3
standard
sysvsem
tokenizer
xml
xmlreader
xmlwriter
xsl
Zend OPcache
zip
zlib

[Zend Modules]
Zend OPcache


Test script:
---------------
any php / custom / wordpress / etc - that produce result longer than 62kb or 82kb

Expected result:
----------------
full page php response.

Actual result:
--------------
any php page is cut to 62-80kbs with ending character ���������