Jools...
Attached find a simplified version of your conveyor...
My Stretch parameter does not impace the Attribute, or the Circle.
Perhaps it is or was an order of operation issue?
I drew the geometry, I added the Circle and then placed the attribute at center.
In Block Editor, I used Far right end of the conveyor rectangle as the start point of the stretch
when defining the Window of objects the action should work on, I was sure to NOT overlap the circle or attribute in any way.
when selecting objects to be stretch the same precautions were applied.
You may have to back up to go forward with this.