+1, Thanks for the 12/20 update.  Its great to have this info!

Just wanted to add that the vst scan is also freezing up on the Waves Studio rack mono

not here, all my waves stuff including all studio rack give no issues

Weird...
I have a bunch of other waves stuff which all seems fine. I can even watch the scan for the StudioRack Stereo plug complete.

Well, suddenly (having done nothing) I ran another VST scan and it actually completed for the first time in 3 weeks. I really didn't even do ANYTHING (no computer reset or anything) just tried running it again and it completed the scan. I can even open the projects with CA2A that I have been trying to work on. I really hope this stays working!!! Fingers crossed.
 

RSMCGUITAR
Well, suddenly (having done nothing) I ran another VST scan and it actually completed for the first time in 3 weeks. I really didn't even do ANYTHING (no computer reset or anything) just tried running it again and it completed the scan. I can even open the projects with CA2A that I have been trying to work on. I really hope this stays working!!! Fingers crossed.
 

Check out my post near the bottom of page 5. Monday things were messed up as usual - runtime errors. Tuesday and today I'm getting no runtime errors. My problems started just like yours 3 weeks ago. I've used only 2016.09. Did you try the VST scan on Tuesday? It looks like the fix is something MS and Cakewalk are working on and has more to do with the internet.

soundtweaker

rwheeler
Shortly after I typed my message here, Windows popped open a message that it would need to schedule a restart. I closed open applications, rebooted, watched the messages about Windows installing yet another update, then watched the reboot happen. Just for fun I tried opening Sonar again. It opened normally. No issue with VST scan. No issue with missing audio device. I opened my recent project to find it working just fine again. Here's hoping this new update actually patched the underlying issue (although I understand the issues have been inconsistent for others, so I won't celebrate too strongly until the improvement clearly persists).

 
I can confirm the new cumulative update (KB3201845) fixed the Plugin Scanning issues for me.

Cumulative Update for Windows 10 Version 1607 for x64-based Systems (KB3201845) did not solve the scan issue.

I don't think it freezes on certain plugins. It hangs randomly and can hang on any plugin. It just does.

Yep, Same experience here. On my system Sonar has been consistently stable throughout the sonar updates as well as all the Windows updates. There must be a common denominator causing these issues on some machines and not on others.

Installed update 2016 12. The scan completed once and found 517 new plugins out of 700 something. I did not install all those "new" plugins. Also it completed scan last night before 2016 12 once but the next time froze again. Strange thing- the... what you call this vertical line that runs during playback? That thing keeps stumble and hang while VST Scan is running, like if it was waiting for a plugin to be scanned. I have many plugins, so it takes long time of hangs and freezes of that vertical "runner" before it gets stable when scan is completed. And I get Audio Dropouts at rest while idle- new finding. Had them occasionally but now it regular- couple times per few hours.