I have a large tablix (Tablix1) with only two cells (top cell for header data, bottom for details). The entire tablix is grouped on dataset field "ParentCode". Header cell shows information about the ParentCode and details cell has a tablix (Tablix2) that shows tabular data about ParentCode.
Issue: The first row of the first ParentCode that appears on the first page = last row of the whole dataset.
I added a dummy table above Tablix1 to push it on the second page and the issue disappears. (This was just something I was trying and not for the report.) Also, issue only happens in PDF export and Print Layout mode of SSRS Report Builder and not the regular report viewer. Issue also doesn't happen when there is only one ParentCode in the dataset i.e. only one overall group.