I'll answer @davoscollective's three questions separately.

First, the query ...

select

[Measures].[Net Lost Commitments] on columns

, ([Date Dimension].[Fiscal Year Hierarchy].[Fiscal Year].Allmembers) on rows

from Compass3

... lists all years from 1899\00 to 2024\25, with correct values (as far as I have tested) for all years except 2004\05 which shows (null).

In my original post, I described a (null) value being shown for 2009\10. Since then I have made minor changes and rebuilt the cube. Every time I rebuild, the (null) value(s) move to different time periods. This time round the correct value is shown for [Fiscal Year].[2009\10] but there are nulls for [Fiscal Year].[2004\05] and [Calendar Month].[Dec-2006].