Comment by Dangeranger

Yes, my AirPod Pros do this too, and I've found that the issue is due to a problem with the external microphones which are involved in active noise cancelling. In order to fix the problem I had to disable ANC, and use them like a pair of basic wireless headphones, which has been quite disappointing. I've found that basically any instance of dropping the headphones on a solid floor, even while in the case, will result in this rattling sound occurring.