i know that using only one stereo output (1+2) the problem is gone,but i've also managed to fix with multiple channels.Try to not use 5/6 just to start.

Ok,i've done several test,i can recreate the issue.
I've just create a simple sonar project with a rewired Reason 7.1.1 project with 1 subtractor to Reason output 1/2
and 1 Thor to Reason output 3/4.
Yout got distorted audio.If you stop the Sonar audio engine and disconnect Thor from output 3/4 leaving only subtractor connected on output 1/2 and after restart the Sonar audio engine (important!) the distortion is gone.
Soon after you reconnect Thor to 3/4 you got distortion.
Very weird issue...
Download the project(s) and try by yourself :

https://dl.dropboxusercontent.com/u/9179211/SonarReasonBugTest.rar
 
 
 

This will be fixed in the 2016.04 release. I think we will be pushing another early access build tomorrow that has this fix if you want to try it out. It was an interleave caching problem - reassigning the reason output on the track is a temporary workaround.

So do you already know about that issue?Is there since months!Please im interested to try the fix before the final update.Thanx.

Noel Borthwick [Cakewalk]
This will be fixed in the 2016.04 release. I think we will be pushing another early access build tomorrow that has this fix if you want to try it out. It was an interleave caching problem - reassigning the reason output on the track is a temporary workaround.

Amazing.. Fingers crossed.
I was really scratching my head.. Thinking that maybe it was my Propellerheads Balance interface (discontinued - no true Win10 drivers).. I was sure it wasnt my CPU/RAM - Not with two instruments and nothing else.

Hmmm...I'll admit I haven't rewired anything in a while, didn't realize a bug had been introduced somewhere along the line. Regardless, I still recommend deleting unused rewire.dll files, because doing so definitely fixed some head-scratcher issues when I was a heavy ReWire user.

Noel Borthwick [Cakewalk]
This will be fixed in the 2016.04 release. I think we will be pushing another early access build tomorrow that has this fix if you want to try it out. It was an interleave caching problem - reassigning the reason output on the track is a temporary workaround.

Tried the early release..
 
Same issue... no fix. 

The updated early access build was posted literally a few minutes ago. If you downloaded earlier you should get it again. The build that has the fix is Early Access 22.4.0.26
 

Confirmed...it's on the list of bug fixes for 2016.04.

Noel Borthwick [Cakewalk]
The updated early access build was posted literally a few minutes ago. If you downloaded earlier you should get it again. The build that has the fix is Early Access 22.4.0.26
 

Apologies.. Jumped the gun..
 
Looks like 22.4.0.26 is not available to me yet,, I only have 22.4.0.23
 
Downloading 22.4.0.26 now