It might be where you needle sits. I have one machine that every time I turn her off, it automatically goes to some weird setting all on its own and I have to play with the (Curvy) to get the needle exactly 1/4" from the little metal bar on the foot of my 1/4"quilting foot. I have a piece of cardboard 3" by 6" that I have one marked the one side exactly 1/4" and every time I sit down at that machine, I put the cardboard with the 1/4' measure next to the foot bar and gently lower the needle to make sure it is exactly at the 1/4" mark, if it does not, I gently click the button that moves the needle till it is exactly 1/4" and also, make sure that I hold the fabric gently so that it maintains its 1/4" all the way past the needle. That works for me, hope it helps