How to stop matrix YYMM columns being filtered?

Hi all

I am trying to build a matrix table, which shows a count over the previous year. The columns in the matrix use a Dates table to populate the YearMonth values in the columns. However, when I filter/slice the rows, the columns with no values are being filtered out. Is there any way to keep the empty columns from being filtered out?

I have a relationship between the data table and the date table (on the date values), where the cross filter direction is set to one way

See below matrix before any of the rows are filtered:

No row filters applied - all columns present

However, when I apply some filters to the rows, the columns with no values are filtered out too:

Filters applied - columns with no values filtered out too

If anyone can help I would appreciate it

Many thanks