I have a “TV Show” that I add a new episode to once a week. When ever I put a new episode in the folder and plex detects it, it does and removes the title for ALL the currently added episodes, even though the field is locked.
It is best to match an available show to prevent this.
If the show can’t be matched - for some reason:
New Agent:
Go to the Show Page and ‘Unmatch’ (under the dots)
I think that will tell Plex to use the Personal Media Agent and stop trying to match this show. I expect to be corrected if that’s wrong.
Old Agents:
Fix Match at the Show Level (under the dots) - Search Options/Select Personal Media (Agent Dropdown) - then select the only item in the list and that’s yours. Plex will no longer try to match the show.
In either case, once you set Plex to stop trying to match - your edits will stick.