Problem with Rank dimension

[#1]

Hello:

I'm not sure whats going on as I have the following calculated dimension that works fine:

=aggr(rank((sum({<Scenario = {'Actual'},GRPCOD={140}>}Amount) - sum({<Scenario = {'Actual'},GRPCOD={'150'}>}Amount)) / sum({<Scenario = {'Actual'},GRPCOD={'150'}>}Amount)),Project)

When I try to use a similar calculated dimension on another table which only is slightly different it doesn't work all the time:

aggr(rank((sum({<Scenario = {'Actual'},GRPCOD={140}>}Amount)) - (sum({<Scenario = {'Project Forecast'},GRPCOD={140}, [Fiscal Year], Month, Quarter, [Posting Date] ={"<=$(=Max([Posting Date]))"}>}Amount))) ,Project)

What I mean by that it doesn't work all the time, is that sometimes based on selections made the sorting isn't as expected as the rank isn't always in the order I expected. I speculate the following "filter" may be the problem?

[Posting Date] ={"<=$(=Max([Posting Date]))"}

Thanks