Here are some thoughts. If the pieced backing didn't lay flat (poofy areas) then some pleating can occur. Your quilter should have contacted you to let you know she was going to have a problem before she started quilting. The quilt backing can't be seen while quilting until it is being rolled as you quilt but the quilter can get a pretty good idea if the backing is going to lay flat or not when it is loaded onto the frame. Just MHO.