Help Required with Removing Visual Filters in Measure

Bit of a strange one this. I have my fact table, Shortfall Items, which is a list of different categories (Works Order, Stock and Purchase Order) and I have this linked to a dimension table for Items, which is essentially a products table with one record per product. They are linked in the model via the item code field.

I then have two tables on a page, one for my items and another for my shortfall items, but that has a visual filter on to only show the category Purchase Order.

The cross filtering works as expected at this point, I select from the items table and the purchase orders table displays all purchase order records for that selected item. So far, so good.

I then needed to create a measure that sums up the Shortfall Items Item Qty field, but not just for Purchase Order records, but for all records in the fact table. On top of this I needed to add a filter to only sum when the date on the fact table record was less than the record in question. Initially I tried the following:

Shortfall Issue Timing Purchase Order Icon = 

VAR po_date = MIN('Shortfall Items'[ITEM_DATE])

VAR qty_cltv_prior = CALCULATE(
    SUM('Shortfall Items'[ITEM_QTY]),
    ALL('Shortfall Items'[ITEM_CATEGORY]),
    'Shortfall Items'[ITEM_DATE] < po_date
)

RETURN qty_cltv_prior

However, this resulted in blank values on the Purchase Orders table:

So then I tried a different method, I changed the ALL() from a specific column to just everything. I needed to add in an additional filter to get this to work so that it only summed for the item being cross-filtered:

Shortfall Issue Timing Purchase Order Icon = 

VAR po_item = MIN('Shortfall Items'[ITEM_CODE])
VAR po_date = MIN('Shortfall Items'[ITEM_DATE])

VAR qty_cltv_prior = CALCULATE(
    SUM('Shortfall Items'[ITEM_QTY]),
    ALL(),
    'Shortfall Items'[ITEM_DATE] < po_date &&
    'Shortfall Items'[ITEM_CODE] = po_item
)

RETURN qty_cltv_prior

This works, as you can see below, but kind of kills performance. It takes a few seconds to load the table when being cross filtered, but if not cross-filtered, can take many seconds to render:

But then it gets weirder. I add on a variable to display an icon depending on whether or not the qty_cltv_prior value is negative or not:

Shortfall Issue Timing Purchase Order Icon = 

VAR po_item = MIN('Shortfall Items'[ITEM_CODE])
VAR po_date = MIN('Shortfall Items'[ITEM_DATE])

VAR qty_cltv_prior = CALCULATE(
    SUM('Shortfall Items'[ITEM_QTY]),
    ALL(),
    'Shortfall Items'[ITEM_DATE] < po_date &&
    'Shortfall Items'[ITEM_CODE] = po_item
)

VAR icon = IF(qty_cltv_prior < 0, [Clock Bad Icon], [Clock Good Icon])

RETURN icon

It returns all of the fact records, not just the cross filtered ones:

I can get around this by filtering on the Qty Due column to only show values greater than zero, but I don't think this is the solution.

Can anyone explain where I am going wrong, possibly in multiple places! Thanks 🙂