I'm experiencing this issue as well. I have some older media on a network share of a pc that I do not use frequently at all. So I only boot it up on demand, and then it would be nice if Emby didn't have to scan this share again and again, after the media becomes unavailable & deleted over and over again.   What kind of failsafe is there? Maybe my setup doesnt't trigger the implementation? I actually only have one library called "Movies" added in Emby. In this library, I added multiple fold