Apache2 crashing - segmentation fault

I submitted this as a support ticket but was told it is outside of their scope to help me. Any help here is appreciated, I’ll buy you a beer or something if you figure this out with me!

Apache2 is intermittently crashing on my Ubuntu server and I’ve done a lot of debugging but can’t find the source of the issue.

Details:

• When the error occurs, my site is down, no output or error message. In /var/log/apache2/error.log I get messages that look like this:

[core:notice] [pid 6113] AH00051: child pid 9744 exit signal Segmentation fault (11), possible coredump in /tmp/apache2-gdb-dump 

• I set up that gdb dump directory and set apache to dump its core before crashing, below are the contents of that file:

Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

warning: the debug information found in "/usr/lib/debug//usr/lib/php5/20121212/mysql.so" does not match "/usr/lib/php5/20121212/mysql.so" (CRC mismatch).

warning: the debug information found in "/usr/lib/debug/usr/lib/php5/20121212/mysql.so" does not match "/usr/lib/php5/20121212/mysql.so" (CRC mismatch).

warning: the debug information found in "/usr/lib/debug//usr/lib/php5/20121212/mysqli.so" does not match "/usr/lib/php5/20121212/mysqli.so" (CRC mismatch).

warning: the debug information found in "/usr/lib/debug/usr/lib/php5/20121212/mysqli.so" does not match "/usr/lib/php5/20121212/mysqli.so" (CRC mismatch).

warning: the debug information found in "/usr/lib/debug//usr/lib/php5/20121212/pdo_mysql.so" does not match "/usr/lib/php5/20121212/pdo_mysql.so" (CRC mismatch).

warning: the debug information found in "/usr/lib/debug/usr/lib/php5/20121212/pdo_mysql.so" does not match "/usr/lib/php5/20121212/pdo_mysql.so" (CRC mismatch).

Core was generated by `/usr/sbin/apache2 -k start'. 
Program terminated with signal SIGSEGV, Segmentation fault. 
<^>#0 0x00007f40b4b86091 in _zend_hash_quick_add_or_update (ht=ht@entry=0x7f40b533d6f0 <executor_globals+432>, 
arKey=0x7f40a05366f0 "/var/www/buydontrent.com/public_html/prod/index.php", nKeyLength=52, h=5705093358713398062, 
pData=pData@entry=0x7fffa37dd408, nDataSize=nDataSize@entry=8, pDest=pDest@entry=0x0, flag=flag@entry=2) 
at /build/buildd/php5-5.5.9+dfsg/Zend/zend_hash.c:279 
279 /build/buildd/php5-5.5.9+dfsg/Zend/zend_hash.c: No such file or directory.<^> 

I assume the warnings are not important, the last few line are probably the culprits. I haven’t even been able to find those files because /build/ is not a directory in my root, so I don’t know where to look. Plus I don’t know C so I’m not sure if I would be able to figure out the problem anyway.

I’ve searched the dregs of the internet for this issue and found one DigitalOcean thread in which users concluded to try a new hosting company (and had success) and some mention of OPCache in another thread, but to my knowledge that isn’t being used on my set up.

Thanks for any help, Mark