Why does DoggCatcher download media files that have been downloaded before?

DoggCatcher will only auto-download the media for new items. So DoggCatcher thinks that the item is new.

Sometimes, feed publishers change the title of the items. By default, DoggCatcher uses the item title to determine uniqueness for an item. So if an item changes its title, DoggCatcher will remove the old item (deleting the media) and add the new item. In this case the media will be downloaded again.

You can tell this is happening if you have items that are marked as done and then after a feed update, they then re-appear new.

Most often this can be fixed by changing the 'item identifier' feed option for the feed to one of the other values. The GUID option is the best choice to start with, but the one that works depends on the feed.