same was the case with me, when the airbag assembly harness started rattling. First they tried to dismiss but on insistence they opened the dashboard (complete). Found one wire set loose from support clamp tat was rattling. Rectified. (Toyota Southern Karachi). This was when the car was not even driven 1000Km
Yesterday there was rattling noise from above the instrument cluster in the dashboard. Complained and the car is taken in for resolution in warranty (toyota eastern karachi).
You have ot be precise and direct the to open the dashboard and rectify the fault. they dont want to do it until unless forced.
I was told that " Sir naee gari hae, poora dashboard khulega, itni si awaz hae". I told them that open it and fix it, and i want it corrected and refitted 100% or i will not accept the vehicle so be careful and the job was done. It took them a day.
Right now the car is again with them but also had a minor accident and have to get the bumper replaced, so will update in about 5 days the status.