Are all your cutters the same brand? If you have changed all their blades at the same time it is possible that you have put them back together improperly. I have kept my original packing for my cutters for that reason. I can never remember the way the washer is supposed to go in my Olfa cuter. Each brand goes together slightly different and they do need the oil that is on them when they come. If we knew the brands we may be able to help more. Once I thought I had a bad blade, it turned out I had 2 stuck together, and another time it was the mat.