My conspired theory is that Evan always waits until this one _would_ get payed and restarts the reference node shortly before it.
I'll call this one "Murphy's Node"
I've just discovered a bug that was only activated after 1000 masternodes were reached. The result is increased variance between payments the more masternodes we get. It's very simply to fix and I'll patch the reference node right away. It'll take a couple days for it to take effect, then we should have pretty even payments again (like after we launched).