The problem is very simple. It has nothing to do with the multiproc updates in JP though it might have appeared so from the symptoms. 
 
I had made a fix for a reported bug in Ipswich for synth recording where some synth multi out channels wouldn't get recorded. That fix resolved the recording issue but it had a side effect of removing an optimization that which skipped unarmed synth channels from the record code. As a result there was some unnecessarily costly code that gets executed for each synth output.
 
The OP's project contains 1024 output ports since he has 32 instances of multiport Kontakt. Now multiply that by 3 for each channelized port (left right stereo) and you see how expensive this is :)
Anyway I have a fix for it. If anyone who has the issue wants to test it out send me a PM.
 
Most users will never run into this since they aren't running with thousands of ports in a project. BTW in the project the tracks are simple instrument tracks so the ports are not even being used. So why not use the simpler stereo version of Kontakt? It will be far cheaper to use and you will not see this load. That is a simple workaround.
 

I can confirm, that the record option "Allow arm changes...." causes the problem on my system.
 
As a film composer I often have a lot of Kontakt and similar samplers open.And often, I need multi-outs of them.


I hope the Cakewalk Devs and Support team, btw best one I've ever seen in DAW development the last years, find a solution to this. And I'm sure they will.
 
@Noel: I'm ready to test your fix and will provide you as much informations I can to support you and Cake-Team.
 
And also a big thank to the community for all your advises, tips and support.
 
best regards
Markus

I'm also happy to test the fix. I don't really use recording from synths, but I do use a lot of samples, typically with multi-out Kontakt, Sampletank, Independence, Play (granted, that one is single-out), multi-track drums, etc.
 
 

Good news Markus but I concur that a fix is needed. 

To clarify most people will not encounter this issue. Its visible only if you have lots of instances of multi out synths in a project and if dynamic arm was on. The OP's project had 32 instances of Kontakt 32 channels each. 
 
Otherwise JP has other optimizations for synths that should improve performance across the board. For example the zero detection now makes multi-out synth processing much more efficient since until the synth is playing the outputs are not mixed in.

I think I can repro...
 
I've got a template with lots of soft synths, each synth has single midi track, however all the synth outputs are being routed to audio tracks. i.e. Addictive drums, Maschine, Kontakt, Geist. To add to the recipe I've got drum maps for all of these from several controllers.


Last tested a few days ago in Ipswitch Update 1 - working fine.
With JP soon as I start playing, sometimes before, it whites out, and after waiting for a while all I can do is close the program.
 
I did manage to get it respond better by deleting the drum maps, however I then ran into the single core issue afterwards...

p.s. Reproduced with dynamic arm off and on! Noel I'll PM you and try it out if I may...
 

Noel Borthwick [Cakewalk]
So why not use the simpler stereo version of Kontakt? It will be far cheaper to use and you will not see this load. That is a simple workaround.

From the Kontakt 5 manual, "The VST plug-in is special in that it comes in 3 different flavors with 8, 16 or 32 outputs."
 
So the smallest would be the 8 output version, right? I don't think a purely stereo one exists.

You may be right. Still 8 vs 32 will make a huge difference. i.e the number of recordable channels changes in the OP's project changes from 32x32x3 to 8x8x3. (the 3 is because every stereo out can be recorded as either left, right or stereo)
I've now optimized the code to handle this much better so its not a hit, but in general limiting the number of channels will reduce load.

brundlefly
Upsampling on playback? When you say "no antivirus" does that include Microsoft Security Essentials?

No upsampling on playback although I tried toggling. Negative on MSE, boot to flash on suspected virus activity.
 
I would enjoy trying the patch although, as I mentioned earlier, I only have a single instance of AD2 running in my project and it's routed to a simple, stereo Instrument track.