Sylenth is acting up only in Sonar... Please see this video for demonstration of the problem
 
https://youtu.be/GZ3Uzdr0icU

I take it the scratchy static sounds aren't what those patches should sound like?  I've heard worse with some synth presets. 
 
I've got Sylenth and Platinum (though haven't used the two together).
 
I've got a busy day ahead, but if no one else has responded or can reproduce, I will test it later this evening.

I can reproduce. I'm getting the exact same thing regardless of what patch is played.

TD75
I can reproduce. I'm getting the exact same thing regardless of what patch is played.

Awesome! Thanks TD75, I hate to say that's good news ... but that's really great news that it's just not me or my system!

My sonar have the same problem.
So I use Jamaica version.
Please solve this problem anybody help me.

Same problem with Ivory II 
 
 

Sorry, couldn't get to it last night.  But good to see TD75 can reproduce.  Has either of you submitted to CW with the steps to reproduce?  It's much less likely to get fixed if it's not reported "officially":
 
https://www.cakewalk.com/Support/Contact/Problem-Report
 

   I can confirm synth problems in Sonar Kingston with iZotope Iris 2 and Novation Bass Station (software synths).  These synths work in Jamaica Plain.  Updated to Kingston and these synths make only static noise.  Roll back to JP, and they work fine.  I did this back and forth twice with this same result.  Report filed with Cakewalk.
   Finally, I just moved to Kingston and stopped using these products.

So far disabling the 64bit Double Precision Engine in Preference > Audio > Driver Settings has solved this for several other synths. Give it a try.
 
When it came to Iris2, I could only make it fail using the VST2 format. The VST3 was unaffected by the 64bit DPE setting.

scook
When it came to Iris2, I could only make it fail using the VST2 format. The VST3 was unaffected by the 64bit DPE setting.

That right there tells me a change was made to VST3 handling in Kingston which had an impact on VST2. 
 
Even as a programmer myself, I could still be wrong.