Hi. I need some advice on what I am doing wrong. I am trying to quilt a lap quilt with simple straight lines across it. I have had to rip out three times because of gathers on the underside (pic of mess is attached). I am using a walking foot and I have basted thoroughly. When I start sewing, it seems like the underside of the quilt is moving faster than the top. I tried lowering the tension because the stitching on top seems too tight. However, when I am ripping out stitches, the thread on the back is so easy to pull out. I can pull out one or two inches by pulling on the thread. I really don't know what else to try.
I'd appreciate any advice on how I can fix this. Thanks so much.