Calculating ITD?

Hey everyone,

I'm having an issue calculating the ITD value of my dataset. It seems like it should be pretty simple but I can't get it to work properly. Here's what my sample data looks like:

I also have a "categories" table:

And I've created a date table with the following code:

Date Table = CALENDAR(DATE(2017, 1, 1), DATE(2018, 12, 31))

I've marked this table as the date table in Power BI Desktop. All the basic relationships between the tables have been set up.

Here's what I came up with to try to calculate the ITD value:

ITD = 
VAR CurrentMonth = MAX('Date Table'[Date])
VAR CurrentCategory = VALUES('Categories'[Name])
RETURN
    CALCULATE(
        SUM([Amount]),
        'Data'[Transaction Date] <= CurrentMonth,
        'Data'[Category] IN CurrentCategory
    )

When I plug that measure into a column chart with no "legend" breakdown, it looks fine:

When I try to add a breakdown by category, it doesn't work as I expected:

It is calculating the ITD for each category but in months where no transaction of that specific category type occurred, it's not showing a bar. I'd like it to always show a bar even if there was no transaction of that category type in that month - it would just be the same as the last month's bar.

Any ideas? I've been banging my head on this for a while now!

Thanks!