Logic Studio / Logic Pro "-10011" error, with almost no CPU or Disk pull

Hi all, I'm expecting my computer to play a session easily. My computer is running a session with (for example) 14 audio tracks, 4 MIDI tracks (using one instance with four layers of ENGINE Miroslav String Ensemble), and 8 Aux busses. I never get any of the other errors or problems associated with a too-slow computer or disk.

Yet, I keep getting the -10011 error. Most times it's "System overload. The audio engine was not able to process all required data in time (-10011)". Sometimes I also get the "Disk too slow or system overload" error.

I have already read through (and applied) the optimizing System Prefs and optimizing Logic support docs. In any case, I'm not even close to the CPU limits with the Logic sessions I'm running.

My CPU and Disk I/O run pretty much in the bottom 10%. When I first press play, the HD meter goes into the red for 1/2 second, then ramps down to as shown. This picture was taken after a system overload error, where it froze on the one core being through the roof.

Normal Playback	After -10011 Error

Clearly some app or plugin is giving my CPU a sudden spike. Can someone point me toward learning more details on which apps or plugins or etc might be spiking my CPU, or what — if other — might be the culprit?

3.5 GHz Intel Core i7

16 GB RAM