Yes there are "Out of Flat" DMT's and the are warranted by DMT so if it is enough to see a gap of light under a Straight Edge then I would return it..

Keep in mind, we tend to put a bit to much emphasis on Flat, but if you pay for Flat you should get Flat...

ps: DMT makes a Plate Cleaning Kit with a Brass Brush a Special Cleanser and a Rubber in there that works rather well, I bought one off e-bay for $8 shipped...