Ok, Yesterday evening I checked what you said starting from the original project with no archived tracks
These are the tests I did
1) I archived the first track (kontakt) using A , I created an audio track inserting the corrispondent audio file that it was already in the Audio Folder ( it was one of the tracks I bounced on Sunday) -> play -> working
2) same procedure with second track ( always kontakt ) -> working
3) third track : I did exactly the same , the only difference was the instrument ( real guitar) -> play -> lots of audio engine stops
Checked : 1) I did no freeze on tracks 2) all input echo disabled 3) disabling effects -> same thing - 4)routing was the same 5) master level ok
So I did another try : I bounced the real guitar vsti track using export from file menu ( On Sunday I did it from Tracks : bounce to tracks ) , after that , I archived the original track -> created new audio track inserting the corrispondent audio file
and.... it worked , play was fine without any problem
Don't know why, to be honest, I didn't have the time yesterday to do other tries and checks but , anyway, this is my solution
and I'm happy with it
Is there any kind of incompatibility with real guitar vsti ? Don't know
Thanks for your kind help
Ramp