Moving contents to a new location but keeping generated video preview thumbnails. Is it possible?

After the copy of the other folders I’m now having issues removing the old content location from the library: I can remove it but after saving, I get an infinite loading indicato for some minutes, then I get the “Your changes could not be saved” error, then Plex becomes unstable.


reloading the web page, I get the old location still present:

I’ve also tried this method but without success.