SCOPE() format_string problem SSAS live

And another example... I've got a calculation defined with a format string. Once I remove SCOPE() assignments, then PowerBI

shows the format string correctly. Otherwise it doesn't.

CREATE MEMBER CURRENTCUBE.[Measures].[Invoice Rowtotal - last year]
AS [Rowtotal LY],
FORMAT_STRING = "#,##0",
FORE_COLOR = 9079434 /*R=138, G=138, B=138*/ ,
VISIBLE = 1 , DISPLAY_FOLDER = 'Revenue\EUR' , ASSOCIATED_MEASURE_GROUP = 'Invoice Line';

SCOPE(DESCENDANTS([Date].[Year-Week-Date],,AFTER));
[Measures].[Invoice Rowtotal - last year] = SUM(EXISTING [Weeks],(PARALLELPERIOD([Date].[Year-Week-Date].[Year],1,[Date].[Year-Week-Date].CurrentMember),[Measures].[Invoice Rowtotal]));
END SCOPE;

SCOPE(DESCENDANTS([Date].[Year-Week-Date],,Leaves));
[Measures].[Invoice Rowtotal - last year] = null;
END SCOPE;

SCOPE(DESCENDANTS([Date].[Year-Quarter-Month-Date],,Leaves));
[Measures].[Invoice Rowtotal - last year] = null;
END SCOPE;