duplicating podcasts and missing podcasts

if I link to any of my previous posts

Where (or how) do you link to those posts?

itunes follows the link and uploads the podcast episode again causing duplicate episodes

The iTunes Store shows only the information from the RSS feed which you have registered there. If someone subscribes via a iTunes client software via the iTunes Store page or iTunes link to your podcast and loads an episode. The listener downloads it directly from your blog. The iTunes Store does host the episodes.

iTunes displays the post title of and not the file name and determines whether a post is new or old with the help of the <guid> value (see https://www.apple.com/itunes/podcasts/specs.html#rss) of each <item> (which represents a post in RSS feeds).
If one is already a subscriber of you podcast and has already downloaded episodes in the past and you do something what modifies the <guid> values then the old episode will appear as new not downloaded episode in the iTunes client software.
That is how it works and why you should avoid measures which modify the <guid> values.

Your observation of the function of the behaviour of the settings which influence the number of posts in a feed is correct.
But I’m not sure that there is something to fix in WP or in podPress. This WP setting changes the number of posts in the feeds. But how modifcations of this value influences the apearance of the list of episodes in the feed reader (e.g. iTunes) depends on the feed reader and how it handles a feed which has suddenly more posts which are older then posts/episodes which one has already downloaded. But it is likely that this program will show older but not downloaded episodes as new ones.

Let me clarify my question. Let’s say that I publish a post on my blog. Within that post is my podcast episode. The Itunes store will automatically display the new podcast episode, which is what we want to happen.

The next day I publish a new post. Within that post I create a link with anchor text that says, “Here is a link to yesterday’s podcast” and I link it to yesterday’s post. the Itunes store will then display the podcast episode a second time, but this time it displays the title of the episode as “Here is a link to yesterday’s podcast”

I hope that clarifies the issue. Any advice on how to fix this?

Okay, I understand a little bit better.

The reason for this behaviour is that WP creates for every link to a media file in a post automatically a custom field with the field name enclosure. When someone requests a news feed, WP uses these meta information to add and <enclosure …> tag to the post in the feed. podPress adds the media file also in such <enclosure>.
The iTunes software recognises only the first enclosure of a post.
That is why podPress usually rearranges the enclosure tags in a way that the podPress attachment comes first.

Which podPress version do you use currently? and which WP version?

On a second thought, it seems possible that a service like Feedburner may reverse the order of the enclosure elements again or removes all but one enclosure and leaves only the last enclosure tag per post in the feed.

However important is the amount of the enclosures and the order of these elements inside the <item> sections of them RSS XML code.

Where and how would I view these enclosures. Today is the first i’ve ever heard of them.

View the XML source code of RSS feed. I’m using always Firefox to do that.
(Open the URL of the feed in the browser. Make a right-mouse-click on the page and select “View source code”. If the URL leads to a Feedburner page then look for a link which says “View the XML code of the feed.” first.)

Firefox will show you the source code which contains besides others

<item>
...
</item>

sections. The first <enclosure ... /> inside such an item will be the media file in the list of episodes in iTunes.

If you route your RSS through Feedburner then it would be interesting to compare the source code of the feed which your blog creates the code Feedburner produces.
I guess Feedburner knows that only one <enclosure ... /> per item is recognized by iTunes and other feed readers and deletes under certain circumstances all but one enclosure per item.
So try to open the Feed URL of your blog in one browser tab and the Feedburner version in a different tab. If the default Feed URL gets automatically forwarded to the Feedburner address then it might be necessary to deactivate the Feedburner plugin (or what ever the forwarding does) for a moment.

Today is the first i’ve ever heard of them.

That is totally okay. If you tell me the name of your blog (or the feed URL) then I can take a look too.

My blog is located at GaryEugeneHowell.com

Well I have compared the default RSS feed (https://garyeugenehowell.com/feed/) and the Feedburner version (https://feeds.feedburner.com/ChristianFictionHostedByGaryEugeneHowell?format=xml) and they include the same posts and episodes.
But I have noticed that the Alison Strobel Interview Recap post is a post which has an enclosure (“https://garyeugenehowell.com/podcast/Alison_Strobel.mp3&#8221; or from the Feedburner version “https://feedproxy.googl…F0/Alison_Strobel.mp3). But this enclosure is one of the automatic enclosure which WordPress adds to the post in the feed (and as an custom field to the post itself).

The default feeds contain all posts. But podPress adds one additional feed to each blog – in your case https://garyeugenehowell.com/feed/podcast . This feed includes only posts with at least one podPress attachment. That is why this feed does not include the post Alison Strobel Interview Recap but instead the older post Alison Strobel Interviewwith the podPress attachment “https://garyeugenehowell.com/podcast/Alison_Strobel.mp3&#8221;.

If your default feed would contain more posts then it would contain both posts. Both posts have the same file attached. That is why there would be two posts with different titles but the same file in the iTunes list.

If you want to avoid this effect, offer the https://garyeugenehowell.com/feed/podcast feed as the podcast feed.
OR
Put a few lines of code into the functions.php file of your theme see https://www.ankitsharma.info/blog/get-rid-of-auto-enclosure-of-media-files-from-wordpress-feed

Ok. I’m going to do the first option and offer the https://garyeugenehowell.com/feed/podcast feed as the podcast feed. Thanks for your help and I’ll let you know if it works.