kiss cuts not cut well

I have used about 60+ stickers of my order of 200. With about half the stickers (so far) the kiss cuts are not cut deep enough. I need to use the tip of a knife to peel up the sticker. There are sometimes spots where the vinyl is not fully cut and vinyl get stretched trying to remove it. Printing looks great, I would order other kinds of stickers from Sticker Mule again, but not kiss cuts.