I agree with the others. I had that happen once. I spent hours & hours trying to get it flat again (heat, cold, pressure, bathtime). It got better, but never even close to good enough for precision cutting. I bought a new one & kept the old wavy one for when I cut with my pinking blade since pinking blades also ruin mats. With a 60% off coupon at JAF, they're not terribly expensive -- though I would have rather spent that money on fabric.