i did a search of the forum and didn't see this issue. here's how to reproduce it:
set "auto add to playlist" to yes. download a few podcasts from different subscriptions. Delete one of the subscriptions.
what i'm seeing is that between every file now in the auto playlist, i get an error saying it's looking for a podcast from the deleted subscription.
so i think the bug is - when a subscription is deleted, remove those podcasts from the auto-playlist.