Force a new discovery of previously misidentified/mislabeled material due to bogus embedded metadata in MP4/M4V files:
To prevent Plex from reading embedded metadata in MP4/M4V files, preventing the issue you are having entirely…
The 4th paragraph is the answer:
Note: if you do this step first, then refresh metadata for the whole show, or a single movie, it’s possible the issue will resolve. Worth a try.
Note: this issue will present for TV Shows and Movies, so moving Local Media Assets to the bottom of the stack for every agent (where applicable) would be wise.