Prior Year Value not calculating correctly

Can anyone help explain why the Amount_PY measure is not returning the correct value in the Full Year scenario below. 

It is summing up amount across all years but I'm just not able to figure out why. 

DEFINE
    MEASURE __Metrics[Amount] =
        SWITCH (
            SELECTEDVALUE ( __Period[Period Name] ),
            "Month",
                CALCULATE (
                    SUM ( Financials[Accounting Currency Amount Signed] ),
                    DATESMTD ( 'AccountingCalendar'[Date] )
                ),
            "Year-To-Date",
                CALCULATE (
                    SUM ( Financials[Accounting Currency Amount Signed] ),
                    DATESYTD ( 'AccountingCalendar'[Date] )
                ),
            "Full Year",
                CALCULATE (
                    SUM ( Financials[Accounting Currency Amount Signed] ),
                    ALLEXCEPT ( AccountingCalendar, AccountingCalendar[Year] )
                ),
            SUM ( Financials[Accounting Currency Amount Signed] )
        )
    
    MEASURE __Metrics[Amount_AC] =
        CALCULATE ( [Amount], Scenarios[Scenario Type] = "Actuals" )
    
    MEASURE __Metrics[Amount_PY] =
        CALCULATE ( [Amount_AC], SAMEPERIODLASTYEAR ( AccountingCalendar[Date] ) )

EVALUATE
SUMMARIZECOLUMNS (
    AccountingCalendar[Year],
    AccountingCalendar[Calendar Month],
    __Period[Period ID],
    __Period[Period Name],
    TREATAS ( { "Latest" }, AccountingCalendar[Month Type] ),
    TREATAS ( { 2022, 2023, 2024 }, AccountingCalendar[Year] ),
    "Amount_AC", [Amount_AC],
    "Amount_PY", [Amount_PY]
)
ORDER BY
    AccountingCalendar[Year] ASC,
    __Period[Period ID] ASC

Note: The Month Type essentially filters the latest completed month within each year.