This is on a shared node and, as far as I can tell, occurs for none of the other clients on the node. I'm fairly convinced that the issue is caused by an add-on, considering your server also idles at 3GB of memory usage...
The best advice I can offer you is to try seriously stripping down your add-ons, and keep disabling more of them until the issue ceases. Maybe also post a console log from after you disabled hatmod.