First thing you should do is fix your naming so that you are following the recommended naming convention as shown here: https://support.plex.tv/articles/categories/your-media/naming-and-organizing-tv-shows/
So in this case, you should have the file named whichever is appropriate as below (where e## should be the episode number)
Heartland - s02e## - The Ties That Bind.mp4
Hearland - s15e## - 4 Sins of a Father.mp4
After you correct that, you should do the Plex Dance to clear out at least those episodes (though as it would be better to update your naming for the whole show, you could dance the entire series).
Your issue almost certainly stems from not following the recommended naming convention by Plex provided in the first link.
-Shark2k
