I do not believe there is any difference between having it as a YTD og periodic, because all values are AST, so there should not be any difference.
I am however 100% sure that my IFRS starter kit has the model to be YTD, however my enviromentshell is Periodic.
I have now create a copy of the Rates model that is periodic, and my script is now working 100% as intended. So i guess the issue is closed.