Behavior
When moving from one master record to another, the related detail datasets should refresh, obtaining a result set that consists only of records that correspond to the selected master. Thus the detail datasets display only the records that are children of the master dataset.
However, the "second" detail dataset does not refresh if the record count of the detail result set is the same for both the prior result set and the new result set.
There is a project at GitHub that illustrates this problem. For those with more curiosity, see the README. Here's the URL: https://github.com/Pasquina/uniguimasterdetail.git