Hello BXRZ, congratulations on your new purchase and welcome to … The Forum .
As far as I recollect, the parking brake rattling, is a new rattle in the FR-S/BRZ, to me at least.
Where is the sound coming from (inside of the car or outside of the car?)
Maybe the rattle is coming from something else (like a shield under the car) and the parking brake is getting the rap?
So, if you are driving down the road and the rattle starts and you gently lift up on the emergency brake handle .. the rattle stops?
Come back.
humfrz