I'm not blaming the 07 update yet, but I have seen more audio engine dropouts in the last week than I have in probably the last year. It is happening under very light loads, sometimes just one instrument. 
 
What's the best way to start diagnosing this?
 
Updates usually seem to reset some of my settings, is there one I'm forgetting that might have changed?
 
Thanks!

I have a post about it as well. I rolled back to the 06 version and initially was stable again. I primarily use ik multimedia, waves, and melodyne plugins so not fully sure what happened. A good starting place is to disable all fx and see if your solid. Then track by track enable them back in. I did end up having some issues with the roll back but after going into each plugins I was solid again. Good luck

Check the preferences for caching and such. 
 
What solved dropout problems for me in the past was clicking on the Help button when the Toast notification popped up showing that audio had dropped out. I went through the recommended solutions and always found one that worked.

Yes same for me, I believe some modifications have been made to the audio engine. It started with the June update,  hearing a harsh noise when i push  the play button,  but playing anyway.  This is a lot worse with the July update and Sonar crashed several times today. The project uses several instances of soft synths and FX pplugins. But never had that before.  Very frustrating. 

let's see if my config is now displayed when I post.

Went through the same here, starting in June, and watched as others posted the same experience. It was intermittent, and I couldn't pin it down. I assume that's why the terminology in preferences, for sharing drivers with other programs, was changed. One of the things I loved about Sonar is that it didn't choke when I had other programs open. I could look up a tutorial or play something through the Windows Media Player while I ate lunch and didn't have to shut Sonar down.
 
After the terminology changed, I could no longer even use Chrome without going back into Sonar and having a ton of dropouts and an eventual crash. Also, the screen went from a smooth scroll to a herky-jerky tug with the music not matching what was on the screen along with generally buggy behavior. Using Windows Media Player resulted in a crash 100% of the time. I've had the same set up, running different version of Sonar for the past six years, and never saw this kind of behavior. I own several other daws, and all of them continued to work as normal.
 
Last Thursday, after doing the Windows update, I decided to look around my computer and see if anything needed to be updated. I keep up on my Windows updates, and my Lynx Two card hasn't had an updated driver in a couple of years. I ran the Radeon check for my card and was behind on updates for the video driver. I updated the driver, and my smooth interface scrolling returned. The mouse wasn't hanging after I pressed buttons. Sonar started as soon as I pressed play instead of pausing. But, I still can't use any other program that might access the audio driver without it introducing instability or a crash in Sonar.
 
Before I updated my Radeon drivers, I did install the Windows update:
 
Microsoft .NET Framework 4.7 for Windows 7 and Windows Server 2008 R2 for x64 (KB3186497)
Installation date: ‎8/‎4/‎2017 1:48 AM
Installation status: Successful
Update type: Recommended
The Microsoft .NET Framework 4.7 is a highly compatible, in-place update for all the previous versions of .NET Framework 4.X. After you install this update, you may have to restart your computer.
 
So, I don't know if this Windows update, the updated Radeon drivers, or both that seemed to solve a lot of the instability I was seeing. But, the program still seems to grind to a halt eventually if I open any other Audio program.
 
On Windows 7 Pro, fully updated.