The fault may be in the EPG data you are receiving. If you are using XMLTV and can check the XML file content, see if the programs that are having this problem are correctly identified as a Series. I'm not at my PC right now so can't tell you exactly what should appear in the XML file, but there is supposed to be a tag to identify series.
Without the correct Series tag, how would MC know that the program was a series and not a stand alone program, if there is also no Episode name? MC probably assumes that a program is a series if there is an episode name, regardless of a missing tag, but without the tag or an episode name it has nothing to go on.
All program's must have a Name, so that would be why the series name is placed in the Name tag, when that is all the information available.