I have the exact same problem with The Endgame (TVDb ID 410357). Every time a new episode is added, Plex ignores the existing match and re-matches the show as Endgame (TVDb ID 228031).
All my folders and files are named correctly (The Endgame\Season 1\The.Endgame.S01E01…). If I do Plex dance, after re-adding the show keeps being matched to the wrong one. I can unmatch it and fix the match manually, but after each new episode is added Plex rolls it back to the wrong metadata, which is absolutely ridiculous. I’m out of ideas…
