Sum Values by condition for the previous months

Here's a much simpler measure that works in all circumstances:

Measure = 
var __tableToIterateOver =
    filter(
        'Table',
        'Table'[BANKED] = "Y"
    )
var __amount = 
    SUMX(
        __tableToIterateOver,
        var __currentDate = 'Table'[Date]
        var __result =
            calculate(
            
                var __prevDateOfBankedStatus =
                    CALCULATE(
                        MAX( 'Table'[Date] ),
                        'Table'[BANKED] = "Y",
                        'Table'[Date] < __currentDate
                    )				
                var __output =
                    CALCULATE(
                        SUM( 'Table'[FEES] ),
                        __prevDateOfBankedStatus < 'Table'[Date],
                        'Table'[Date] <= __currentDate
                    )
                return
                    __output,

                // Leave only the filter on Fund.
                ALLEXCEPT( 'Table', 'Table'[Fund] )
            )
        return
            __result
    )
return
    __amount

Best

D