We have discovered that if you have a granite or marble counter top under your rotary mat, that your blades dull very quickly. Don't know why -- it doesn't make sense. But several ladies have come to the same conclusion. Don't know what you've got under your mat, but you may want to try cutting on a different surface.
Also, if you're not using the same brand of blade, as your cutter, the center hole is different, and causes the blade to jerk.
I hope you find a solution.