How to make audition stop mix down all tracks, when trying to save a PR file in AU

Hi

I started working on a PR file by dragging in into AU, it shows all individual, sperate tracks perfectly. But when I save the file in AU by "file -- export -- export to adobe premiere pro -- with 'export each track as stem' ticked, I got an mixed down file.

Is there settings i can change to make Audition save it as a file with all tracks sparated, and can be edited individually?

Thanks