Straight-up, a roll of 651 white, (whether new out-of-the-box, or a little bit older) is the only color I have to absolutely increase the force on, whether on my LP or Graphtec.
I do have to add a little more force to some of my older 651 colors, but not when they're new.
I just chalk it up to, "It is what it is." I know I have to do it, so I can get clean cuts that are easy to weed.