Server Version#: 1.29.0.6244 on a Windows desktop
my existing library language has been changed to empty and can’t put it back to french
not only is the language drop down empty but can’t change any setting (tells me “can’t be saved”)
also, movies posters are are now cropped and in landscape instead of portrait
Only 1 of my libraries is impacted
Any clue what’s happening?
Most likely the metadata agent of that library got changed to “Personal media” at some point in the past.
Try changing it back using the hosted web app.
Make sure your web browser doesn’t have any browser add-ins activated which could interfere.
Additionally, verify that your server’s database file is in good health.
-
activate debug logging (not ‘verbose’!)
- quit Plex Server
- wait 1 minute
- start Plex Server
- wait 5 minutes
-
fetch log files and attach them here
Or inspect them yourself. Take a look at the Plex Media Server.log file and seek for messages about database corrupt or malformed.
If you find these, you may have to repair your database.
https://support.plex.tv/articles/repair-a-corrupted-database/
Same behavior in the hosted web app: language “none” too
Here are my logs
Plex Media Server Logs_2022-09-28_14-32-02.zip (3.3 MB)
thx!
in the hosted web app, whatever I do, it keeps on coming back to “personal media” agent 
The above settings have nothing to do with your issue.
Edit the library, like shown in your second screen shot.
Try setting the agent to “Plex Movie (Legacy)”.
Is this successful?
setting can’t be saved so it stays on “personal media”
(read circle in my screenshot showing “can’t be saved” message in french
Then I’m afraid that your movies library is messed up beyond repair.
All you can do is creating a new library, with agent Plex Movie selected right from the start (it is the default, anyway).
just realized library type has been changed to “other video” type and not movies (which is greyed anyway.) Gives hopes for a fix or dead?

That change is a direct result from selecting “Personal Video”/“Personal Media” as the agent.
An “Other Videos” library is actually a Movies library, just with a different agent.
got it but why can’t change it back to movie type with plex agent instead?
Probably because the change is also a change in metadata agent “generations”.
“Plex Movie” is the new world, whereas Personal Media is the old world.
You are not the first where changing between them is a one-way road.