Wonder if the grinding is an unwanted side effect of the low rpm shifting (fuel economy tune) causing some unwanted harmonics in the powertrain. Still should have been caught during testing.
My '12 and the '11 TDI in my sig with 6 spd DSG, the programming lets it lug along at 1100-1200 RPM in some driving situations which causes a pretty obnoxious grating/grinding/rattling sound when giving it a little bit of throttle to maintain speed. Same "fix" is to drop it into sport which then keeps it in gears to keep engine speed closer to 2k RPM.
My '12 and the '11 TDI in my sig with 6 spd DSG, the programming lets it lug along at 1100-1200 RPM in some driving situations which causes a pretty obnoxious grating/grinding/rattling sound when giving it a little bit of throttle to maintain speed. Same "fix" is to drop it into sport which then keeps it in gears to keep engine speed closer to 2k RPM.