If you are using Magento 2 and you got this 500 error from admin login page. Your Content Security Policy header are too long. Use Nging or reduce your headers.
Problem is AP_IOBUFSIZE cannot be changed by a conf file it is hardcoded in to the sourcecode. You have only 8192 Bytes and this os offen to low. If you reach this limit your apache willcrash and restart.
Look at the Bugzilla from Apache Webserver