Thank you for trying to help, it is really appreciated.
I have been in and out of a clients recording session all afternoon and this evening so I have only just got the chance to reply.
I can confirm that the articulations you have used are the ones I used except I used except I was using standard legato (not performance) to save on CPU but so that we are both using the same I will do the following tonight.
I will create a new blank project in Cubase pro 12 with the same settings as you.
I will add one instance of Kontakt as a Track Instrument, and one instance as a Rack Instrument.
In to each Kontakt I will then load -
5x Kontakt 6.7.1 tracks (vln1, vln2, vla, cello, bass) each containing one SF Chamber Strings Performance Legato.
5x Kontakt 6.7.1 tracks (vln1, vln2, vla, cello, bass) each containing one SF Studio Strings Performance Legato.
This way we are both testing with the same.
When I can tomorrow (we have sessions booked in all day), I will screen capture it as video (with sound) so you can see the settings within CB 11 & CB 12 are exactly the same and will then play back my MIDI files.
This way you can see and hear the issue happening rather than me trying to describe it.
I can also zip up the CB 11 & CB 12 project files and MIDI Files together with the plug-in Reports that Matthias has asked for so that you can see everything.
Due to another CB 12 issue where my Arturia MiniLab mk II has stopped working after installing the v12.0.20 update (it worked perfectly before), I have performed a clean fresh install of v12.0…00, v12.0.10 and then v12.0…20 as admin so all previous Cubase preferences have been (backed up as Matthias suggested) but then deleted from the system.
So for the test I have fresh install of CB Pro 12.0.20 Build 263 and the only 3rd party plugin is Kontakt 6.7.1.
I can also confirm that even when I had all of my 3rd party plugins installed my CPU usage was quite low, as was memory usage.
With the fresh Cubase 12 install the CPU and Memory usage is even lower but the issue still happens.
I appreciate you trying to help me and I hope that the video will let you see and hear what is going on.