Diagnosis
Something hard—a piece of bone, glass, a pit, or even a loose screw—has gotten past the filter and is being tossed around by the wash arm or, worse, is stuck in the wash motor's circulation pump.
How to Fix It
Immediately cancel the cycle and let everything settle. Unplug the machine. Remove the lower rack and the filter assembly. Use a flashlight and look all around the sump (the plastic basin at the bottom). Feel around with your hand for any foreign objects. Then, manually rotate the lower spray arm. Does it spin freely, or is it hitting something? Check the holes in the spray arm for blockages.
If That Didn't Work
If the noise persists after a thorough clean-out and with an empty tub, the circulation pump itself might have a damaged impeller or bearings. On these models, a failing pump can make a metallic grinding sound. That's a component-level repair that typically needs a technician.
Heads Up
Seriously, scrape your plates. The "Linear Wash" filter is good, but it's not a garbage disposal. Hard debris is the number one cause of pump failure and these pumps are not cheap. If you hear a new, persistent noise, don't just run more cycles hoping it'll clear—you'll likely make the damage worse.