If I have an existing podcast or two in an individual feed that I haven't listened to yet doggcatcher will overwrite the audio from the older podcasts with the new ones while leaving the title and description the same. For example, most recently in the podcast Conan O'brian Needs a Friend the podcast app listed the three episodes I hadn't yet listened to as Colin Quinn, Michelle Obama Returns, and Rory Scovel, however all three had the audio for the Colin Quinn episode. This has happened on several different individual feeds.
See FAQ post about this issue to resolve the problem http://www.doggcatcher.com/node/6613