Podcasts: Old episodes retained permanently in unaccessible format

[I posted this issue before, but iPad auto-correct made a bit of a mess of it, so I'm reposting with fewer errors...]

When I select Podcasts in iTunes, it displays a total episode count as 213 episodes, taking up 10 GB worth of space. When I created a Smart Playlist with Media Kind > is > Podcast, it displays 806 episodes. Some are 1 KB files that I already played and they should have been deleted (I assume the 1KB files ate just pointers to those files). Most, however, are the full file size, adding up to 42 GB worth of podcast files.

These have also been played (except the 213 noted above) and the Last Played column and Get Info confirms their Played status. Selecting one of these podcasts does not give the option to Delete them. Get Info does show the Finder path to the episode, but the Podcasts folder in Music > iTunes does not contain the file.

Podcast settings:

Show is set to: Unplayed/My Episodes and Saved)

Episode settings: Delete Played Episodes.

My questions:

1. I'm having huge problems with Podcasts re-downloading old episodes as if they have not been played;

This occurs over and over again, even after manually deleting them;

2. How do I clear this mess?

Un-subscribing, then re-subscribing the podcasts has no effect;

Changing the Media Kind to something other than Podcast, so at least I can delete them, doesn't help, as these deleted episodes

reappear shortly thereafter;

FWIW, there are other posts about this issue, so it's not unique to me.