Our supplier has a quality test procedure in which a flat glass was used to test the balance of our keyboards in the factory to make sure the keyboards are flat. The keyboard itself has silicone rubber stands on the bottom to make it lay flat on the desk. We also tested it extensively in our office. You may try to put it on different desks to see if it's still uneven.
If the problem persists, please kindly shoot a video showing how the keyboard stands/wobbles with and without the adjustable legs on an EVEN GLASS SURFACE (table, window, etc.), we will check it out and try our best to help you with the problem. Thank you.