Go to:
Settings/Agents
Drag Local Media Assets to the bottom of every active Agent list under Movies and Shows Thusly:
(Red is where it is now - Green is where it needs to be - do NOT disable LMA - ur gonna need it, just not where it is)
Plex is reacting to embedded and bogus info in the Title Field of your MP4/M4V file and after 140 years Plex still hasn’t learned the default location of LMA is - WRONG.
You’ll have to hack that mistake by fixing it for them.
You may need to Plex Dance afterwards - if after moving LMA for all Agents under TV and Movies - Refresh Metadata does nothing.
All Steps, In Order, Exactly as described (or it simply won’t work):