I had this issue and contacted XLN about it. When using addictive keys I would get that crackle. I tried to find the emails in the trash but couldn't. I just remember that the .dll file had to be replaced. Contact them to help with that unless you can do it. I was told to delete the file(s) and re install them from the online installer. Go to (advanced) and see the path that they install to and delete them. Then I remember to run the vst scan in sonar to refresh it. Then go back to the installer and re install the keys. I had no problem with AD drums, just the keys. For you I would imagine I would do both. Hope this helps

Cactus Music
Are the offending VST's 32 bit? 

 
Yes, they are.
 
 

sharke
Do you use f.lux by any chance? It has been the cause of many unexplained crackles among those who work with audio on PC's.

No, I'm not a user.

msmcleod
If it's only started happening since the Windows update, try uninstalling/re-installing your audio drivers.
 
You might want to re-install your graphics driver too. I had the same issue, and it was the re-installation of the graphics driver that fixed it.

 
Believe me, I have. It was a sweat show, but that war is over.

OK simple, don't use 32 bit plug ins on a 64 bit version of Sonar unless you want issues. Either find 64 bit replacements or install the 32 bit version of Sonar. Bit Bridge is well know to not work all the time. And for me it causes Sonar to crash randomly on any project I was still running 32 bit plugs. I hated to have to stop using my beloved Mr Tramp but that's progress, gotta keep movin on. 

Cactus Music
OK simple, don't use 32 bit plug ins on a 64 bit version of Sonar unless you want issues.
 

That did it! Thanks so much Mr. Cactus
 
Also, Mr Tramp, God rest it's soul.

Cactus Music
 
but that's progress, gotta keep movin on. 

 
That seems at odds with your recent leading of the charge to keep SONAR locked away on a frozen system for years into the future? You don't see the 2 at odds?, something a little off here? perhaps a little selectivity in practice?, one might even dare say hypocrisy? just a little mind you, . . .  you know just a smidge,  . . . a hair,  . . . just a tickle?
 
Amazing, these forums never cease to provide, the SONAR faithful are always good for a good old belly laugh, far better value than a night out at a comedy festival, and it's continuous daily impromptu performances. . . hilarious 

Glad it worked. 
It's too bad some of those good old freebies never got ported over to 64 bit. 
I had a pretty big collection of 32 bits that I liked a lot.  But I found a lot of good stuff now in the Air Expand pack which you can pick up cheap when it goes on sale. It's also amazing what we have in just the included Sonar stuff. I think Sonar will go down in history as having the best collection of included content. 
 
 

ccable

Cactus Music
OK simple, don't use 32 bit plug ins on a 64 bit version of Sonar unless you want issues.
 

That did it! Thanks so much Mr. Cactus
 
Also, Mr Tramp, God rest it's soul.

Or, as I said, if your 32-bit plugin is indispensable, convert it to 64-bit using JBridge (https://jstuff.wordpress.com/jbridge/).

crackles are usually always down to wrong buffer size.