I am running on Centos 7 and having a strange but very minor issue, if a static file such as css or image is missing on the filesystem, Apache will return 500 instead of a 404.
I've tried a few things such as temporarily disabling selinux, mod_security, and mod_pagespeed to narrow down the issue, and the logs are not giving me any indication as to what rule would be causing it to return 500 instead of gracefully returning a 404.
Does anyone have any ideas for ways to find the cause of the 500 errors being thrown?
Edit (add log samples):
modsec_audit.log
--f9f2f74b-F--
HTTP/1.0 500 Internal Server Error
Content-Length: 0
Connection: close
Content-Type: text/html; charset=UTF-8
access_log
[09/Jun/2015:19:38:37 -0400] "GET /subfolder/images/BTN_red_bullet.gif HTTP/1.1" 500 - "http://example.com/subfolder/" "Serf/1.1.0 mod_pagespeed/1.9.32.3-4448"
error_log
[Tue Jun 09 19:09:28.612497 2015] [pagespeed:warn] [pid 18574] [mod_pagespeed 1.9.32.3-4448 @18574] Fetch timed out: http://example.com/subfolder/images/BTN_red_bullet.gif (connecting to:x.x.x.x) (1) waiting for 50 ms
