The incorrect episode titles are stored in your files.
Your first example used MKV, so I didn’t mention the possibility of ‘embedded metadata’.
But Plex can read embedded meta tags from m4v and mp4 files and will even use those preferably over data from the online sources.
Do this:
Go to
- Settings - Server - Agents - Shows - TheTVDB
In there, grab the line ‘Local Media Assets’ with your mouse and drag it downwards, so it ends up being at the bottom of the stack of active agents.
Repeat the same under
- Settings - Server - Agents - Shows - TheMovieDatabase
- Settings - Server - Agents - Movies - Plex Movie
- Settings - Server - Agents - Movies - TheMovieDatabase
Afterwards, ‘Refresh Matadata’ of the affected series.