New FE 50mm F1.2 GM - makes a thunking sound

[ST]

I just picked up a new FE 50mm F1.2 GM.

I noticed that when the lens is not mounted on the camera when I turn over (end over end) slowly, I hear and feel a quiet thunk inside. It's like something heavy inside is moving on rails. It's not a rattle.

I think I feel the same thing when the lens is mounted on the camera (A1), but that seems to stop when I turn on the camera.

I have other Sony lenses, but this FE 50mm F1.2 GM is the only one that does this.

Is this normal?

Should take this back to the authorized Sony dealer where I got it?

Thank you.

[pm-r]

I know this can be freaky but this is 100% normal.  Some of your other lenses "clunk" too but you may not have noticed.  This is totally OK and it's supposed to be like that.  Worry not!!!!  The 501.2GM is really noticeable but my 85GM, 135GM, and 400GM all do the same thing.  There is nothing wrong 🙂. pm-r

[ST]

3 hours ago, pm-r said:

I know this can be freaky but this is 100% normal.  Some of your other lenses "clunk" too but you may not have noticed.  This is totally OK and it's supposed to be like that.  Worry not!!!!  The 501.2GM is really noticeable but my 85GM, 135GM, and 400GM all do the same thing.  There is nothing wrong 🙂. pm-r

Thank you @pm-r
After checking closely, I hear it with my FE 70-200mm F2.8 GM OSS II. It's not as noticeable. 
All the best.

[pm-r]

you bet!!!!