Apple Podcast app. Broken since iOS 14.5 and not fixed since, despite Apple admitting the Apple is horrendously flawed.
Apple
is aware:
"Over the last few weeks, some creators have experienced delays in the availability of their content and access to Apple Podcasts Connect. We've addressed these disruptions and encourage creators experiencing any issues to contact us.
We've also heard from listeners and made adjustments based on their feedback with iOS 14.6, which was released on Monday. We will introduce additional enhancements to Library in the coming weeks."
UPDATE: Some saying this does not apply as issue pre-dated iOS 15. Many people thought that the issues would be addressed in iOS 15, therefore have not even upgraded to iOS 14.5 (the version that broke the app). I am posting this to wiki so those waiting to upgrade until the app is fixed know that iOS 15 has NOT solved the issue.