When you make changes be sure Plex picks it up.
A good way to do that is to perform the “Plex dance” after you make changes.
The following is from earlier and some of the steps may no longer be needed.
“Plex Dance” to force Plex to reread the media files correctly.
…
Move the folder or files to a location where Plex cannot see them
Force a scan of the library
Empty trash
Clean bundles
Move the folder back into the library
Force a scan of the library
…
Be sure to do each step above in order and allow each step to complete before doing the next and do not skip any steps.
Also before you do the above be sure the agent “Shows” has “Local media assets” moved below everything else.