RELATED IDEAS
Don't Group By Filters when the field isn't in the Report
When you add filters to a report like "Goals" and a feature is associated with more than 1 goal it duplicates the lines in the report. However, when the field that you are filtering on is NOT in the data set it shouldn't be grouping by this field at all. The display should only group on the fields that are returned as part of the dataset.
Unfortunately because of how reports are implemented this will not be possible.
You can workaround this limitation by using a Reports -> Pivot rather than Reports -> List and only show the unique items in the pivot table.