ᐅ My shelving unit gets new stains after every cleaning – how can I prevent this?

I have a rather unusual problem with my Kallax shelf from IKEA: every time I clean it, new stains appear that weren’t there before. These marks look like water rings or small water spots, but they remain visible even after drying. I usually use a slightly damp cloth and then let it air dry. Obviously, something isn’t quite right – maybe a reaction with the material or a cleaner that leaves residue. Does anyone have any ideas on how to prevent new stains from appearing on the Kallax after each cleaning? I would appreciate concrete tips covering factors such as cleaning methods, suitable products, or the material itself.