The platen on my new, unused belt sander (R2740 3x18) is not flat. The little support nibs underneath are set up to be higher on one end than the other, and the two sides (lengthwise) are high on opposite ends. One side of the platen is fairly flat but the other side is quite concave. I've only used the sander once to see if the odd, not-flat pattern shows up on the wood surface and it sure does. What's up with that? I noticed this issue on one sander I bought and I took it back unused to the store and picked up another one...same thing. So I tried it...as I mentioned the uneven pattern ends up on the wood surface.