Episodes list showing Artwork when filtered Season 1 but not showing Artwork when filtered as unknown.

I was trying to help this podcast with updating Artwork for their Episodes. It looked as a lot of the new the episodes had no artwork.  Even thought there was 165 pictures updated to The Dead Meat Podcast page on IMDb.  If its filtered by "season: unknown" there isn't that many episodes with artwork. If I change the filter to "season: 1" then the artwork shows up.  You can see what I mean with this link.  https://www.imdb.com/title/tt15433220/?ref_=ttep_ep6 Then there a link showing the same episode as new with review in the title but as episode 10 with no picture. https://www.imdb.com/title/tt16855902/?ref_=ttep_ep10 

Is this a IMDb tech service thing they need to fix. I don't what to be trying to do double the work trying to update to listing per episode.