Audio Track isn't Sforzando a one patch at a time instrument?
I thought that it was, however I don't use it thus I don't know.
If it is a one patch at a time instrument then it is not GM compliant.
Mario, yes, you are correct if it can only play one patch at a time, it doesn't meet the full GM spec.
I don't specifically use Sforzando so I give no assurance and no guarantee that my offer of assistance is going to resolve the issue. But I hope it helps in some small way.
Often we see that users have made multiple adjustments to their settings. I was hoping that starting from a baseline might help identify / resolve the O/P's original issue.