Deep grooves in the brake discs

Hello guys, I have been in possession of a Toyota Verso Edition 1.8L since 28.02.2007. At 500 km of mileage, three brake discs have seen deep grooves in the middle of the brake surface. In the workshop, all brake discs and pads have been renewed at 2100 km. Now at the mileage of 3120 km, at the rear brake discs, again deep grooves in the middle of the brake surface are visible (between 0.5 and 0.8 mm). Is anyone familiar with a serial problem with the BOSCH brake pads?