Originally Posted by Pati- in Phx

If a new blade is skipping, it may be your mat.
when you cut you need to be sure that the blade is perpendicular to the mat, not leaning at all. When the blade leans for one cut and another cut goes through the "angle" you get a "divot" in the mat. You may not even see it, but it is enough to leave a gap that doesn't get cut.
Try turning your mat over. <G>

You also want to be careful to not cut at the same place all the time. Move around on your mat, rotate the mat and so on.

And mats do wear out. We sometimes have to replace them.

When the blade skips at the same interval on a long cut, it's the blade.

Have fun,
Pati, in Phx