Tell me more about the sub summary. Is it a trailing or leading one? Also, try moving the fields in the sub summary down 1 pixel just to make sure they are not in the header.
It is a Sub Summary when sorted by Month Name. However, after selecting I am presented with "Print Above" and "Print Below" options with "Print Below" the default. After selecting "Print Above" it works just fine. Thank You.
PS: I still think it is sort of a bug.