I don't know if the following is old news. It wasn't for me therefore I post it.

I think all of you had the prob that some of the sealed PS4 games arriving in the mail had a loose disc inside. It seems to be a common problem with PS4 cases. (I disliked this rittling-rattling noise) Here is a way to fix this problem without opening the game. (If you like to keep games sealed until you play them, like me)

It works like a charm, is incredibly easy, I used this method already on 5 PS4 games.

For the following youtube video you have to turn up the volume, but he was the first to post it. He deserves the credit, therefore here is the link:

LINK: https://www.youtube.com/watch?v=mIdlgFOdfAk