I’m not too fond of Rotten Tomatoes. Their reviews are awful and wrong. I have IMDB selected as cast, ratings, and plot summary, but Rotten still appears as the rating source on the initial movie screen.
How do I get rid of RT once and for all appearing in any way from Plex?
Is that movie matched using the Plex Movie (legacy) agent?
From what I know, Plex might fall back to ratings from different sources if it cannot find one from the primary/preferred one. Though that particular movie clearly seems to have a rating on IMDb
The reviews have nothing to do with the rating source.
Plex does not offer an option to disable those. However there’s a few threads dealing with how to manually delete those reviews in the database (manually or via scripts).