Mamiya 7 lens making a wierd noise... normal?

Hey, so i got this Mamiya 7. When i take off the lens, and move it around a little bit, i hear a wierd noise, kind of like ball bearing moving around or something ( ? ), a really quiet creaking noise.

Upon a little bit of research it seems like it's normal... but i want to be sure. Can anybody confirm this? Does your lens make that noise too?

And if it is normal, i'm curious to what causes it. People who know a lot about leaf shutters, feel free to enlighten me.

Lens making noise, not body, btw.

there is, inside the lens, a ball bearing ring which IIRC rives the diaphragm.
If the ring isn't full of balls (like my 80) makes that sound, to me no issues so far in the last 5 years I've owned and heavily used that lens, and made that sound since the very first day.