Since these are MP4 files they could have embedded metadata which is overriding the information provided by the online sources. To prevent that from occurring, try lowering “Local Movie Assets” in priority in your agents configuration under Settings → Agents → Shows → TheTVDB/The Movie Database:
Leave “Local Media Assets” enabled, but move it lower in the list than your other enabled sources. After that, perform the Plex Dance on the series in question:
Alternatively, edit the metadata tags in the files and ensure the information in there is correct or just delete them. And then do the Plex Dance.
