I'd start with checking if there were any errors in your logs when you performed the upgrade or installation. It may be difficult to track down since this would be an internal process to ColdFusion. It could be the mail spooler, CF cleaning up sessions, caches being invalidated, etc. I'd suggest something like FusionReactor would be able to help you here. You could also expand your search to other logs around the same time and see if any activity there gives you a hint of what is happening at that time.
Hi Nic --
No, there were no errors upon install. This appears to be something wrong at the server level.
It just happened again a few minutes ago, and from the looks of it it's an issue stemming from "SESSION CLEANUP AGENT". Wish I knew what was going on here. I have submitted a bug report on the tracker site but haven't heard anything back. My primary concern is that these errors are leaving corrupted sessions hanging around, or leaking memory, or otherwise creating long term stability issues for the server.
"Error","scheduler-2","08/04/17","17:51:21","","'' The specific sequence of files included or processed is: '''' "
I agree with you, @Terry_2011_. There seems to be a bug in ColdFusion 2016's session apparatus.