Filter on calculated dimension in Qlik Sense

[Anonymous]

I have two related fields in my load script:

[Positions]:

FundCode

,InvestmentCode

,round(fabs([Duration])) AS HedgeDurLong

[Investment]:

InvestmentCode

,InvType

,round(fabs([Duration])) AS HedgeDurShort

Then in my calculated dimension (a master item):

if(InvType = 'SWAP_IRS', HedgeDurShort, HedgeDurLong)

[Investment] has a 1 to many relationship with [Positions] (i.e., one investment can have many positions).  Using my master item, I am able to make charts/pivots with it just fine.  But I cannot use this dimension as a filter.  I click on it, the UI flashes, and refuses to filter the data.  What's going on?