iTunes Library Management with NAS

Hello Community,

I've got some issues with my iTunes Library Management.

I've got my Time Capsule (5th generation) working as my router and a NAS and signing the IP Adresses to my devices.

Also got Back to My Mac activated so I can access my Time Capsule remotely.

I've got my whole iTunes library stored on this device, so whenever I add a movie/song in my iTunes it copies it on my NAS.

So the issue is sometimes my whole library is gone and my the destination to my iTunes library is in the music folder

and I have to pull everything back in so I can see them in iTunes.

I hope someone can help me with the issue of my stuff always vanishing from my iTunes.

Is there a program that scans the iTunes library and updates the movies/music in my iTunes?

Thank You

PS: The access speed of remotely streaming movies/songs from my Time Capsule is pretty slow. Is there a better solution to that?