Unwanted podcasts showing up in Listen Now

This started a couple of weeks ago. In the Listen Now section of the podcast app, under the Up Next header, I'm getting episodes for podcasts I'm not subscribed to nor have ever been subscribed to. I may have listened to one or two episodes from the podcasts, but I never subscribed, and I never relistened to the episodes. Usually, episodes I download are removed after I've listened to them. But now I'm bombarded with episodes for every single podcast I've ever listened to. Which is really annoying. How can I get the podcast app to stop doing this?