DIAGNOSIS A foreign object is interfering with the QuadWash spray arm rotation.
FIX
1. Stop the cycle and remove both the upper and lower racks.
2. Manually rotate all spray arms: the two upper arms, the middle arm, and the lower arm. Check for free movement.
3. Inspect the spray arm holes and the wash tub floor for debris like bone, glass, or utensil fragments.
4. Remove the lower filter assembly and check the impeller area of the wash pump for obstruction.
IF THAT DIDN'T WORK The wash pump motor bearings may be worn out, causing the grinding sound. This requires pump replacement.
HEADS UP The middle spray arm on QuadWash models is particularly prone to catching large items like measuring spoons. Ensure no tall items are blocking its path.