Drilled rotors make noise during stops. It's a "feature".

Even the PFC 'Direct Drive' rotors on my M3 make a subtle grinding-like sound.

Granted, you should check that everything is ok and no debris is between the pad/rotor, but likely it is the nature of the beast.

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Kirk
Las Vegas
2016 X5 40e Mineral White/Black Dakota Leather, ZLL, ZCW, ZDA, ZDB, ZPP, multi contour seats, rear side window shades, HK stereo
2011 E90M3, 6-speed manual