MoM calculation help

[MrToast20]

I am trying to create a MoM calculation but the result is incorrect.

Background

Data files are generated each month and imported to sql.
The test dataset is for Jan & Feb data files

The Feb datafile includes all the Jan data + feb
The data has a column dataFileCreationDate

For Jan the dataFileCreationDate is 31012024

For Feb the dataFileCreationDate is 29022024

Each data row has a processDate which is the date the transaction was processed on the source system

Each data row has a UWYear column which is the year of the transactions inception.  This is a slicer on the page

Both datasets include record with processDates back to 2020

dates[Date] is the dates table and is related to items[dateFileCreationDate]

The page has a filter where date = 29/02/2024

Measure

Prior Month Cost = CALCULATE(Sum('Items'[Cost), PREVIOUSMONTH(dates[Date]))

issue

Prior Mont Cost is correct when the slicer has the current UWYear selected - 2024. 

If I select a different UWYear in the slicer, e.g 2023, the calculation is incorrect as it includes transactions that were processed in feb24.  it should only include those from the previous month - Jan24.

Guessing I have something not linked correctly here, any help appreciated.

Thanks

[MrToast20 · Accepted solution]

This turned out to be a data anomality when reconciling reports. This can now be closed

[lbendlin]

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