Considering the show itself is already matched, Plex should be able to recognize the new episodes ok. That being said… always go with the described naming schema. Everything else is set to fail at some point.
TV Shows <- the folder linked to your tv show library
Friends
Season XX
Friends - sXXeYY - optional episode title.ext
Friends - sXXeYY.ext <- without the optional episode title which will be ignored by Plex anyway
...
(where XX is the season number, YY the episode number and .ext the file extension).
Now… as for your imminent issue. You seem to be using MP4/MV4 files with embedded title tags (title probably shows the name of the disc this was ripped from → “FRIENDS SEASON 3 DISC 1”) in combination with Local Media Assets being prioritized over your other sources in Settings > Server > Agents.
To fix this… either clean your MP4/M4V files and get rid of the obnoxious embedded titles… or decrease the priority of Local Media Assets for the TV Show agent you’re using. https://support.plex.tv/articles/200241558-agents/