Matrix column hierarchy breaks calculations in values

Hi there!

Odd one with a Matrix visual using a hierarchy I have created.

If I drill up or drill down my column hierarchy (to view one level at a time) the numbers in the Matrix are correct. But as soon as I expand to the next level (to see both levels of the hierarchy), the numbers switch to adding up cumulatively regardless of the column in the visual:

The relationships are fairly simple (I think): One descriptor can have multiple bands, each band can have multiple scores. I have taken this approach because I need to include a table with arbritrary numbers in from another source (the national data):

Is this a relationship problem? 

Thanks in anticipation!