DIAGNOSIS Yeah, this one's common. That's typically bearing noise from the drive coupling—the part that connects the motor to the blade assembly. It wears out or gets debris in it.
FIX The fix is almost always replacing the blade assembly (Breville calls it the 'Blade & Sealing Ring Assembly'). It's a single part. You have to remove the jar from the base, then use the provided wrench to unscrew the blade unit from the bottom of the jar. Screw the new one in hand-tight, then give it a final quarter-turn with the wrench. Don't overtighten.
IF THAT DIDN'T WORK If a new blade assembly doesn't fix the noise, the issue might be with the drive socket on the motor base itself. Inspect the black plastic coupling on the base where the jar sits. If those teeth are chipped, worn, or cracked, the base needs service.
HEADS UP That blade assembly isn't designed to be taken apart and re-greased by you. Trying to lubricate it yourself can contaminate your food and rarely fixes the underlying wear. Just replace the whole sealed unit.