In my experience, when your memory is hovering at *almost exactly* the maximum allocated to your Nagios Log Server instance, a crash becomes much more likely. It would be a good test to pitch up the allocated memory by at least a little. I recommend doubling it, but bumping up to 20GB could be helpful as well.
TwitsBlog Show me a man who lives alone and has a perpetually clean kitchen, and 8 times out of 9 I'll show you a man with detestable spiritual qualities.