Some times the issue can be caused due to wrongly fitted brake pads. In most cases they won't tight the bolts with torque wrench. These bolts are very sensitive. It may start giving non uniformity on the contact surface and can cause lot of problems. If the problem persists even now show the vehicle to TASS and ask them to inspect it again. For short cut they may use air tools to tighten the screw which is never to be done. Non uniformity of surfaces will lead to non uniformity in heat conduction and can lead to uneven temperature distribution on discs. Better to resolve the problem early before it getting multiplied. Ideally with new pads there should not be any problems. Also I hope you have avoided hard breaking after changing the new pads which we do when we get a new vehicle.