I service small appliances and that exact noise almost always traces to one of three things. Cross threaded blade collar, dry or seized blade bearing, or a coupler that is rubbing the motor shield. Easy checks at home. Hand tighten the blade collar until snug then back off a hair so the gasket is not crushed. Spin the blades by hand. If you feel little clicks or hear squeal, that bearing is done right out of the box.
Fill the jar halfway with warm water and a drop of soap and run a five second pulse. If it still grinds through liquid, the load is not the cause. Look under the jar while it runs and watch the coupler. If it wobbles or walks up and down, that is misalignment. Nothing you did. I tell people to return those immediately because running a misaligned coupler will chew the motor in days. Works great after a clean swap.
