Diagnosis
If you’ve confirmed the floor is solid and the feet are properly leveled and tightened, the suspension rods that hold the inner tub might be weak or damaged. They act like shock absorbers.
How to Fix It
The first thing to try is a redistribution test. Pause the cycle during the spin when it starts banging. Open the lid (it will stop), and manually redistribute the clothes evenly around the basket. Close the lid and resume. If that consistently fixes it, it’s a loading technique issue. If it still happens with a small, evenly distributed load, the suspension is suspect.
If That Didn't Work
With the machine unplugged, you can do a push test. Press down firmly on opposite sides of the inner basket. It should have firm, even resistance and spring back smoothly. If it feels loose, wobbly, or one side is mushier than the other, the suspension rods or their springs are likely worn out and need replacement.
Heads Up
Consistently running an out-of-balance washer puts tremendous stress on the cabinet, drive components, and floor. Don’t ignore it; you’ll cause secondary damage.