Thank you all for your input.  I'm going to pay a bit closer attention to how I move around my cursor and mouse wheel while playing back as well as confirming if the behavior is isolated to just the L3 or other plugins..  I liked the idea of automating the L3's threshold level so that it stays put. 
 
Thanks again.  I'll report back to this thread if I find that the problem persists.

Hello, sorry for the delayed response.  I found the problem some time ago. 
 
What happens during my mixing phase of a project is that I'm going back and forth between tracks and tweaking the volume fader level.  Apparently if I'm not paying attention, I am reducing the fader for the wrong track.  In this case the Master fader was reduced.  This has happened to me a few times now and I can't quite pin point if it's user error or a s/w glitch.  I've been using Sonar for ages and this never use to happen.  But I'll pay particular attention to my work flow and my mouse click behavior to see if a mis-click or if other weird behavior is the culprit.  
 
Thanks for the advice.