Apple Podcasts might be downloading old episodes due to your podcast settings. Here are a few reasons why this might be happening and how you can fix it:

1. **Subscription Settings**: If you're subscribed to a podcast, your settings might be set to automatically download all episodes, including old ones. To change this, go to the podcast page, tap on "Settings", then "Custom Settings", and finally "Download Episodes". Here, you can choose to download only the most recent episode or not download episodes automatically at all.

2. **Unplayed Episodes**: Apple Podcasts automatically downloads unplayed episodes. If you haven't listened to older episodes, they may still be downloading. To stop this, go to "Settings", then "Podcasts", and turn off "Download Episodes".

3. **Re-subscribing to a Podcast**: If you unsubscribe and then re-subscribe to a podcast, Apple Podcasts may download old episodes again. This is because the app treats it as a new subscription.

4. **Podcast Update**: Sometimes, if a podcast host updates or re-releases old episodes, they may appear as new in your feed and be downloaded again.

Remember to also check your storage space. If your device is running out of space, it might be a good idea to limit automatic downloads or delete episodes after you've listened to them. You can adjust these settings in the Podcasts section of your device's settings.