Rolling average monthly. Prob: Considering previous year[month].

Hi,

I'm trying to calculate rolling average, but facing problem when year changes. 

It's considering previous year while calculation.

Finding rolling average of "Cost per pair -USD" and Costper pair usd = [Total Epenses] / [QTY]

It is showing .21 (Rolling Avg.) instead of .18 (Year changes, So fresh cal.), higlighted with red line. It is because of considering previous month result 

I used Quick measure in power bi for rolling average.

Rolling Avg. = IF(
ISFILTERED('Dummy_Table'[ETA]),
ERROR("Time intelligence quick measures can only be grouped or filtered by the Power BI-provided date hierarchy or primary date column."),
VAR __LAST_DATE = ENDOFMONTH('Dummy_Table'[ETA].[Date])
VAR __DATE_PERIOD =
DATESBETWEEN(
'Dummy_Table'[ETA].[Date],
STARTOFMONTH(DATEADD(__LAST_DATE, -12, MONTH)),
__LAST_DATE
)
RETURN
AVERAGEX(
CALCULATETABLE(
SUMMARIZE(
VALUES('Dummy_Table'),
'Dummy_Table'[ETA].[Year],
'Dummy_Table'[ETA].[QuarterNo],
'Dummy_Table'[ETA].[Quarter],
'Dummy_Table'[ETA].[MonthNo],
'Dummy_Table'[ETA].[Month]
),
__DATE_PERIOD
),
CALCULATE([Cost per Pair], ALL('Dummy_Table'[ETA].[Day]))
)
)

 Expected result.

When I tried in excel it look like. It was just simply with formula. 
Instead of .21 I want .18, as year changes from 2017 to 2018.