To explain what is happening here …
Plex uses a consolidated metadata approach, pulling data from multiple locations into a single set of metadata per item, be that a movie, tv show or episode. This data is pulled from sites like tmdb, tvdb, imdb and a private supplier gracenote. Plex then gives admins an option to reorder the episodes based on how the different sites list these episodes (aired, dvd etc…). TMDB is also the default, well 99% of the time, there are some exceptions but not many.
Knowing this here is the important bit. One of the main ways plex does this is by taking advantage of the linkage from tmdb → tvdb for each episode. That way if tmdb and tvdb have different orders and if they are linked between the two sites plex can reorder the episode based on this.
Lets look at an example. Take the s05 episode The Original Fry Cook. This is S05E13 on tmdb and S05E02 on tvdb. When you look on tmdb for the external ids linking it from tmdb → tvdb its missing …
… this means plex has no way to link the ordering which is why its all messed up when you pick dvd order. They most likely have some logic in their back-end try and guess what they are but as you have seen its not accurate.
The fix for this is easy and you don’t need anyone from plex to fix it, you can do it yourself. Just add the external ids for each and every episode at tmdb, linking it to its tvdb counterpart, wait 3-5 days for plex to pickup the change and then you should be good.
EDIT: I’ve gone and reviewed, updated and added missing external id from tmdb → tvdb for all seasons. Give these updates between 3-5 days to be processed by plex and then force refresh the show. It should fix the problem but if it doesn’t then update this thread and I’ll look again.
