When I’m in the Library and do a search with the top-left toolbar (write some text and hit “enter”), I see the results popping up and it seems fine but after a second all of theirs artworks are gone and it’s all grey.
With what app (+version) are you experiencing this?
If you’re using the browser version… are you using the bundled web app (through your server’s IP address) or the hosted web app (https://app.plex.tv/desktop)?
I’ve tried to reproduce the behavior you have described but couldn’t…