First of all please upgrade to kernel 18.104.22.168.
It may not solve *this* problem, but it will fix vulnerabilities.
Second this is no security question and so should better be in Linux - General with your old thread
and I will move this thread there. If you think it's beneficial to merge the two threads ask
You haven't posted much info to go on like when/after which changes this started happening, CPU and process specs, dmesg, HW, drivers, SW in use, etc, etc and the kernel should start spewing messages right after and before activating Out Of Memory killing. Since in your old thread for instance sendmail shows a reject because of high load I don't think the stats you show are useful. I would suggest running continuous stats with vmstat or install more comprehensive tools like Dstat or Atsar, removing all non-critical services from restarting (not syslog and friends but httpd, mysqld, y'know), rebooting the box after installing the latest stable kernel and start monitoring. If it doesn't crash (wait and use the box for say half a day) enable each service, use it and wait a reasonable period (say half a day) before reenabling the next service. When you crash the box you've got some nice dstat numbers to graph in OOo Calc to draw conclusions from and a more approximate idea what the culprit(s) could be, but that's just my 2 cents.