periodic cumulative measure does not respond as expected

[acordes]

I want to aggregate for the upcoming next 12 months, so the calendar year shouldn't impact at all.

My first choice was the periodic cumulative measure but I cannot sum over the next 12 months. This goes against my understanding what this measure promises to do.

My workaround is to sum relative periods (0 to 11 by 1). This works but feels complicated.

Here comes the code for the aggregated measure outlook 12 months that fulfills the task. 

CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 1, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 2, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 3, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 4, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 5, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 6, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 7, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 8, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 9, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 10, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 11, 1, _Full_, {Date}) +
CumulativePeriod(_Sum_, 'Frequency'n, _IgnoreAllTimeFrameFilters_
, '_FECULVTO'n, _ByMonth_, _ByMonth_, 0, 1, _Full_, {Date})