Description:
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From manual page: http://www.php.net/opcache.installation
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The page recommends using directive opcache.fast_shutdown = 1, however this directive is known to be broken. See the following Zend bug which has remained unsolved since 2013: https://github.com/zendtech/ZendOptimizerPlus/issues/146

In my experiences on many clients' servers, fast_shutdown occasionally caused PHP<->web server communication to fail and the PHP process to crash in random places without a segfault. In a number of cases, this led to database corruption. Disabling opcache.fast_shutdown always resolved the issue.

Since opcache.fast_shutdown bypasses PHP garbage collection in favor of Zend MM garbage collection, it is likely that Zend MM is not doing this successfully, possibly creating a Use-Again-Without-Free? situation which causes the next process to crash. However, without segfaults to provide information, this is only a theory.

Expected result:
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The documentation should not recommend opcache.fast_shutdown = 1 until the Zend bug is fixed: https://github.com/zendtech/ZendOptimizerPlus/issues/146

If the Zend bug is fixed, the documentation should specify which version(s) of PHP the fix applies in, and therefore which version of PHP opcache.fast_shutdown becomes safe to use again.