I submitted the following to the forum, and it was suggested that I enter it as a bug:
I have a subreport that has 2 columns, and the way the data falls will make the first column shorter than the 2nd column because the 2nd column has more rows in its group. (I use a group with isStartNewColumn="true") to get the 2nd column started.
When I run the report by itself, it is fine. When I run it as a subreport, the subreport ends up generating one more page because it makes the 2nd column the same height as the first column and the remaining extra rows ends up on the first column of a new page.
I can split this into 2 subreports (one for each column on the main report), but I would prefer to just have one subreport with one query.