New cassette noise

Hi all, I’ve recently purchased a new 12 speed Shimano 105 cassette to run on my new Canyon Speedmax (which runs ultregra 12 speed) on a Tacx Neo 2t.

I’ve installed and torqued the cassette. There’s definitely no play but it’s making a noticeable rattling noise when I’m pedalling, loudest in the middle sprockets. Check the video to hear the sound.

Any ideas for what it is, or how to fix it? Is it just a new chain on a new cassette, that will go away in time?

I’ve reinstalled the cassette twice to make sure it’s tightened and not imperfectly threaded.

I’m hoping that combination of components and trainer isn’t the issue, but someone might tell me otherwise.