Looked at this a little more. Both TVDB & TMDB are doing things kind of weird. They both have a show called “Super Friends (1973)” This show seems to be set up as a collection of all the friends shows. “Challenge of the Super Friends (1978) is listed as Season 3 in this “show”
But each also has each of the “seasons” listed as separate shows.
The easiest fix for this is create a “Super Friends (1973)” folder if you don’t already have one, then move your “Challenge of the Super Friends” folder under “Super Friends”, You’ll need to rename your file to reflect that it is Season 03, i.e. S01E01 → S03E01, S01E02 → S03E02 and so on. If you keep the named “Challenge of the Super Friends (1978)” vs “Season 03” it evens picks up the correct poster. I’ve got it set up like this in my testing library and it is working.