Diagnosis
The blade assembly bearing is failing or debris is trapped in it. The six-point star blade assembly is a sealed unit.
How to Fix It
Unplug the base. Remove the jar. Unscrew the blade assembly from the jar (turn counter-clockwise). Inspect the rubber sealing ring. If it's torn or missing, replace it. Check for food particles lodged between the blades and the bearing housing. Rinse the assembly thoroughly. Reattach firmly.
If That Didn't Work
The blade assembly bearing itself is worn out. You'll feel side-to-side play or grit when spinning the blades by hand. The entire blade assembly (part # BFP-703-BLA) must be replaced. Do not attempt to oil it.
Heads Up
A damaged blade assembly can leak liquid into the jar's drive spline, causing it to seize onto the base. Replace it as soon as you hear grinding to avoid a bigger problem.