It seems that the problem could be that the quilt sandwich is not properly done. The backing needs to be taught, but not stretched, the batting smoothed out well. When I use batting that is natural fiber (not polyester) I press it so that it is smooth. Then, the top needs to be smoothed carefully. I like to use Elmer's school glue for making my sandwich. I work in sections on a 3 X 8 foot table. I use clips on the edges of the table to hold it snugly. If you have to use your hands to push away potential puckers you are pushing that fabric somewhere else that is unnatural and probably want to form another pucker. Also, others have also suggested things to check on your machine to be sure it is set up correctly. I also sew around the parameter of the quilt 1/8 inch from the squared up edge before beginning the quilting process. This adds a measure of stability and disappears into the binding seam at the end. Hopefully, there are some helpful hints here.