Title is somewhat misleading. It's not for anything video-related. It's for using a (probably free) photo of actress Cuca Escribano without permission.
The same photo is still in use by The Movie DB, one of Plex’s data suppliers.
So someone submitted a copyrighted image to a 3rd-party user-created database and Plex ingested the image.
Seems like the claimant has a legitimate case but it's strange that they didn't sue the people actually providing the image. Not enough money in it, probably.
Whether they win the case or not, Plex should replace the photo with one poorly drawn in MS Paint as an FU to the photographer.
Most people use the service for perfectly legitimate purposes.
But also, the copyright infringement is for using a picture of an actress on their website; the photographer who took the photo usually licenses it for third party use, and Plex didn't have permission to use it.