It often gets out of balance when washing large loads. Tonight it sounded fine when running a load of towels, but it is completely full of water at the end of the cycle.
I would bail out the water and shine a light in the spin basket, might have ingested a towel between the tub and basket. You might not see the towel, so I would unscrew the screws holding the lid down, tilt it back and remove the tub plastic top, and fish out the item with a coat hanger.