quilter1943

I still use my Pfaff for small quilts. Might be your needle or thread. I find it's best to use same weight/brand of thread on top and bottom on both my Pfaff and my Mega Quilter. Just helps keep the tension better.

CoyoteQuilts

The number one and two reasons you get wonky stitching on the back is that you either forgot to put the pressure foot in the darning foot position (on my Pfaff you need to push the pressure foot lever back while lowering and catch the 1/2 way hook) or you have the pressure foot down when you threaded the top thread and it isn't in the tension discs.