Function Unreliable with Sets
If you create an expression that uses the descendants function
with sets, you may encounter unpredictable results. Some expected
members may be missing or may have blank captions or labels.
This problem occurs if the descendants function uses a set as its first parameter instead of a single member and if the descendants function is nested under another data item from the same hierarchy.
To avoid this problem, replace the first parameter in the descendants function with the function currentmember(H), where H is the hierarchy of the desired set and under which the expression is nested. For example, use descendants(currentmember(H).