If it is sewing fine when you are not frame quilting you may have an issue with how your quilt is loaded in the frame or a problem with how high you have your take up roller set. You may have the quilt loaded too tight on the frame. Or the spacing is incorrect for the sandwich and the machine bed. This topic, although for a different problem, had loads of great suggestions:
http://www.quiltingboard.com/main-f1...m-t267687.html
PS, edited to add welcome to the board.