Trouble showing Sub-Episodes (eg. E15, E15a, E15b)

Looks to me like your ignoring Plex Naming Convention for TV Shows and that’s an Epic Bad Idea:

Public Enemy Number One is poor naming and structuring:
http://support.plex.tv/articles/categories/media-preparation/
Pay particular attention to TV Show Naming and Structuring.

FileBot (link in my signature) can handle that for you automatically or manually in seconds.

What FileBot can’t do is remove possible embedded metadata in the Title Field of MP4/M4V files. Plex will read this info and prefer it over a perfect file name/structure, but you can combat that situation by moving Local Media Assets to the bottom of every agent list you can find. All tabs in TV Shows and Movies here:
https://support.plex.tv/hc/en-us/articles/200241558-Agents
Just drag LMA to the bottom of the list and drop it. If you do have embedded metadata this will cure the issue, if you don’t it won’t matter. LMA will do what it has to from the bottom.

Renaming/restructuring is best performed OUTSIDE the library and you may need to write a new bundle for the show or movie so The Plex Dance® was invented:

The Plex Dance®:

  1. remove show/movie from library
  2. rescan library files
  3. empty trash
  4. clean bundles
    https://support.plex.tv/hc/en-us/articles/200392106-Library-Actions <— scan library files, empty trash, clean bundles
  5. bring names and structures into compliance/Move LMA/etc
  6. replace corrected show/movie into library
  7. rescan library files

All Steps. In Order. No Shortcuts.

Still No Joy?

Log Files:
https://support.plex.tv/articles/200250417-plex-media-server-log-files/
Drag zip file to message window and drop it.

I could test that naming, but unfortunately you didn’t bother to cough up the name of the Show you’re trying to match - which is pretty important info, when you get right down to it.

If you want the least amount of pain and suffering in your Plex Career, you’d better stick to the naming convention and know that TVDB is ALWAYS right - even if they’re wrong. TVDB is the ONLY TV Show Database so your naming/structuring options are VERY limited.