I love my June Taylor ruler. But there was a learning curve to using it.
I have to make sure my cutter is straight up and down. I guess I usually hold it at a bit of a slant left to right.
I also just pull the slot open a bit when putting my cutter blade in, then let it go and hold that piece down well while cutting.
I made a few nicks and scratches at first, but now we're dancing together just fine.