Unaccounted listing in Profiler

I've been unable to find an adequate answer to this, so if someone could shed some insight into what's going in I would be appreciative. I'm using Unity 5.4.0f2 (64-bit) on Windows 10, for a VR game.
I have 3 scenes, Main scene, Game scene, and Extra scene. Main and Extra are rather small. No issues there, but with my Game scene, where most of the meat of the game is, I'm getting a really bothersome "Unaccounted" listing taking up way too much of my CPU Usage (see screengrab). Spikes to 90% of my CPU Usage aren't uncommon.
Unaccounted does show up in my Main and Extra scene Profiler views, but at a more reasonable 6%, give or take.
How am I supposed to optimize if even the Profiler doesn't know what's going on? Does this refer to some VR stuff that doesn't yet have a proper name?

 

Yup, known (http://issuetracker.unity3d.com/iss...cts-associated-with-them-just-shows-n-slash-a) and we're seeing if the fix will land in f3, or maybe a patch.

 

Great. I'm in no hurry, so I can wait.
Just glad to know it's not just me.
Thanks!