[JGuth]

You just have to change the disk allocation when you save a session made from a template.
There have been many requests to fix this. So it becomes good ( and boring ) practise to check the disk allocation every time you open a new session from a template. OR put the template on the drive you want to write audio to, open it, edit its disk allocation to that drive.
save the template. Then you don't have to do it every time.