Okay to start “Rust is a type of corrosion that occurs on metal surfaces when iron reacts with oxygen and water. The chemical reaction that causes rust is called oxidation. The oxidation process eats away at the metal and creates visible rust on the metal’s surface.”
Have had a quick search on Google and there are a few cooker rusting issues listed on Martins Money site and a couple of others to. I havn’t delved in deep to see if any resolutions were achieved.
Looking at your picture closer I wouldn’t be surprised if the manufacturer said it’s down to moisture ie pans boiling over etc. As your cooker is under 5 years old you do have a five year parts cover so it may well be worth a try contacting them.
Don