Wrong cover for movies

Hello,
I have an problem for which I cant find a solution.
I tried different scanners and agents, all the result… At the moment I use Plex Move as Scanner and Plex Movie as Agent. Prefer local metatags is not activated.

When I add new movies, they will be added fine with correct cover from database. I have some movies (mP4), which will be not added correct. Allwys the same movies. The metatags will be added correct from the Plex Movie DB. But only not the cover. The Scanner ignors the cover from the DB and seems to take a picture directly out from movie.

Is it possible that MP4s have pictures inside the file and plex prefer this ? I mean could there be a tumbnail inside the MP4 ? How can I say to plex to alwys ignor this and alwys load the cover from the Online-DB automatically ?

Thank you and sorry for my bad english

yes.

in the advanced setting of the library disable prefer local metadata

Thank you for your reply.

I want that plex always takes the cover from the Online-DB (in my case Plex Movie). The problem is that plex always takes the thumbnail from the movie-file. I tried both options checked and unchecked of local data prefer.
If I understand everything right, the prefer local data should be unchecked that plex takes the cover fom the agent.

correct

okay but in case there is also the problem that plex ignors this and take the thumbnail from the movie as cover

then i would need specifics about the thing you are trying to add.