SamePeriodLastYear Totals not correct, but each month is.

[TheBIGuy_PBI]

Hi, I have a matrix where i show 3 columns; this years sales, Previous years sales and YOY% Diff, using the DAX formulat SAMEPERIODLASTYEAR. All three columns are measures.
The month over month results are accurate, but for some reason my totals are not correct. the Previous Years Sales is the same as This Year Sales, and the example below shows that each month I do show different results.
Has anyone seen this before?

Here's a screen print of my description above