Diagnosis
The motor bearings are failing. The 1200-watt motor spins at very high RPM on settings 7-10. Worn bearings cause this distinct metal-on-metal grinding.
How to Fix It
There is no user fix for failed motor bearings. The motor must be replaced. This is a core repair that involves disassembling the base and removing the motor assembly from its mounts.
If That Didn't Work
Ensure the noise is not coming from the jar. Run the motor base without a jar. If the noise is gone, the issue is with the blade assembly bearing. Replace the entire blade unit.
Heads Up
Continuing to use a blender with failing bearings will completely seize the motor. The repair cost often approaches the price of a new unit. This is a wear-out failure for high-use blenders.