I recommend you to simply use the default Plex Movie agent.
You can enable the .nfo importer as an additional data source, so Plex movie can “fall back” on it.
I disabled all Plex scans… It takes Plex 14 hours just to scan the movie library…
With the importer its down a few hours, and it makes all my servers identical something the Plex scans never did.
It also enables me to use a media manager that works…
I’ve noticed with Version 1.16.2.1321 that not all metadata is picked up by Plex.
Not sure why, but if I have Plex refresh media metadata it doesn’t get all the changes.
It takes many refreshes… That may be part of the problem here…
When I have some time I’ll post my configurations…